Entity Framework 基本概念

概念

LINQ to Entities	一种 LINQ 技术，使开发人员可以使用 LINQ 表达式和 LINQ 标准查询运算符，针对实体数据模型 (EDM) 对象上下文创建灵活的强类型化查询。
ESQL	Entity SQL 一种与 SQL 类似的、独立于存储的语言。该语言直接操作概念实体架构，并支持实体数据模型功能，如继承和关系。
EF	实体框架ADO.NET Entity Framework 一套支持面向数据的软件应用程序开发的技术，可让开发人员使用映射到数据源中的逻辑架构的概念模型。
EDM	实体数据模型(Entity Data Model) 一个数据模型，用于将应用程序数据定义为公共语言运行时类型和存储结构可以映射到的实体和关系集。
Entity	实体 ADO.NET Entity Framework 应用程序域中的一个概念，数据类型在该域中定义
csdl	概念架构定义语言 Conceptual schema definition language 一种基于 XML 的语言，可用于定义概念模型的实体类型、关联、实体容器、实体集和关联集
ssdl	存储架构定义语言 Store schema definition language 一种基于 XML 的语言，用于定义存储模型的实体类型、关联、实体容器、实体集和关联集，经常对应于数据库架构。
msl	映射规范语言 Mapping specification language 一种基于 XML 的语言，可用于将概念模型中定义的项映射到存储模型中的项

ADO.NET Entity Framework

架构

ADO.NET Entity Framework分Storage Provider ，Mapping Layer ，Object Services，LINQ to Entities 四层。

Storage Provider	负责直接和数据源通讯，支持的数据库Sql Server
Mapping Layer	数据库概念层和逻辑层的映射。通过EDM模型和mapping provider，应用程序将构建在更高层次的EDM模型抽象层次上。同时，在应用程序中将不再使用本地数据库的查询语言比如（T-sql),取而代之的将是Entity SQL。
Object Services	Object Services 的目标是消除数据和应用程序代码风格的不匹配 ADO.NET允许将查询结果呈现为行和列记录，同时也可以呈现为.NET对象。该层还包括了更多被O/R mapping框架支持的高级的服务，比如身份认证，跟踪对象状态变化，并行性检查以及处理更新。
LINQ to Entities	将Entity Framework与LINQ项目集成，以提供面向对象编程语言适合自己特点的查询功能。 LINQ to Entities这一层依赖于object services和mapping layer这两层。

说明

ADO.NET Entity Framework 的数据访问方式与ADO.NET 有类似之处

ADO.NET	ADO.NET Entity Framework
SqlConnection	EntityConnection
SqlCommand	EntityCommand
SqlDataReader.	EntityDataReader
SqlDataAdapter	ObjectContext
DataSet	ObjectQuery<T>
	Entity
	csdl,ssdl,msl

注意:ADO.NET与 ADO.NET Entity Framework是不同的技术,这个对比只是一个帮助理解的比效

EntityConnection

EntityCommand

通过EntityDataReader 方式的数据访问

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection();

econ.ConnectionString = econString;

EntityCommand ecmd = new EntityCommand();
ecmd.CommandType = CommandType.Text;
ecmd.Connection = econ;

ecmd.CommandText = "select it.ItemID,it.ItemMatter from myContext.DBItem as it";//esql

//或

// cmd.CommandText = "select value it from myContext.DBItem as it"; //esql

// to SQL : "select * from DBItem"

econ.Open();

EntityDataReader eReader = ecmd.ExecuteReader(CommandBehavior.SequentialAccess);

while (eReader.Read())

{

Console.WriteLine("{0},{1}", eReader[0].ToString(), eReader[1].ToString());

}

通过ObjectContext返回ObjectQuery<T> 方式的数据访问

ObjectContext提供了管理数据的功能

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);
ObjectContext context = new ObjectContext(econ);

context.DefaultContainerName = "myContext";
ObjectQuery<DBItem> queryTab = context.CreateQuery<DBItem>("DBItem");
foreach (var r in queryTab)

{

System.Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);
ObjectContext context = new ObjectContext(econ);

ObjectQuery<DBItem> queryTab = context.CreateQuery<DBItem>("select value it from myContext.DBItem as it where it.ItemID='a'");
foreach (var r in queryTab)

{

System.Console.WriteLine("{0},{1}",r.ItemID,r.ItemMatter);

}

模型结构

[概念模型]中要有[实体键], [实体键]要与表中的 [主键] 对应,也就是说表必须要有主键.

表中的[唯一键]不会在[概念模型]中体现

在[概念模型]中默认是不允许修改[实体键]的值的

联合主健可以正常映射

如果为属性赋值超过字段长度保存时,会向数据库提交,数据库会返回错误

联合主健的主外关系可以正常映射

只有基于主健的主外关系可以在模型向导中自动建立

Conceptual Model		概念模型用于描述实体(Entity)类型及其关系
Storage Model		存储模型用于描述数据库实际存储架构
Mapping Specification		映射规范将概念模型和存储模型连接起来，以便进行操作转换
Entity Class		实体类用于描述实体的属性，每一个实体类都会定义一个属性或多个属性为一个键属性（Key Properties），用于唯一标识一个实体实体类型可以通过继承关系加以扩展
Entity Set		实体集实体（Entity）存在于实体集(Entity Set)中，就像表格中的行存在于表格中的一样
Entity Containe		实体容器, 实体集定义在实体容器（Entity Container）中
关联		关联定义了实体之间的关系,可以直接通过关联，来访问相关联的对象,关联分为一对一、一对多、多对多关联通过Association Type来定义,过实体类中的Navigation属性就可以访问与实体相关联的实体

模型关系说明

模型设计器结构说明

EDM

EF 没有采取 LINQ to SQL 基于Attribute映射的做法。

为了适应变化和提供更多的数据库类型扩展,EF 提供了专门的定义语言来完成模型设置

Conceptual schema definition language (.csdl)
Store schema definition language (.ssdl)
Mapping specification language (.msl)

默认,Model设计器将(.csdl)(.ssdl)(.msl)存放在一个名为(.edmx)的XML 格式定义文件,并会根据设计自动生成对应的Context与实体类

Model设计器

数据库中的表
模型
模型生成选项

edmx文件

	<?xml version="1.0" encoding="utf-8"?> <edmx:Edmx Version="1.0" xmlns:edmx="http://schemas.microsoft.com/ado/2007/06/edmx"> <!-- EF Runtime content -->
	<edmx:Runtime>
存储模型	<!-- SSDL content --> <edmx:StorageModels> <Schema Namespace="myModel.Store" Alias="Self" Provider="System.Data.SqlClient"ProviderManifestToken="2008"xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator"xmlns="http://schemas.microsoft.com/ado/2006/04/edm/ssdl"> <EntityContainer Name="myModelStoreContainer"> <EntitySet Name="myTab" EntityType="myModel.Store.myTab" store:Type="Tables"Schema="dbo" /> </EntityContainer> <EntityType Name="myTab"> <Key> <PropertyRef Name="a" /> </Key> <Property Name="a" Type="nchar" Nullable="false" MaxLength="10" /> <Property Name="b" Type="nchar" Nullable="false" MaxLength="10" /> <Property Name="c" Type="nchar" MaxLength="10" /> <Property Name="d" Type="nchar" MaxLength="10" /> </EntityType> </Schema> </edmx:StorageModels>
概念模型	<!-- CSDL content --> <edmx:ConceptualModels> <Schema Namespace="myModel" Alias="Self"xmlns="http://schemas.microsoft.com/ado/2006/04/edm"> <EntityContainer Name="mySets"> <EntitySet Name="myTab" EntityType="myModel.myTab" /> </EntityContainer> <EntityType Name="myTab"> <Key> <PropertyRef Name="aa" /> </Key> <Property Name="aa" Type="String" Nullable="false" MaxLength="10" Unicode="true"FixedLength="true" /> <Property Name="bb" Type="String" Nullable="false" MaxLength="10" Unicode="true"FixedLength="true" /> <Property Name="cc" Type="String" MaxLength="10" Unicode="true" FixedLength="true" /> <Property Name="dd" Type="String" MaxLength="10" Unicode="true" FixedLength="true" /> </EntityType> </Schema> </edmx:ConceptualModels>
映射	<!-- C-S mapping content --> <edmx:Mappings> <Mapping Space="C-S" xmlns="urn:schemas-microsoft-com:windows:storage:mapping:CS"> <EntityContainerMapping StorageEntityContainer="myModelStoreContainer"CdmEntityContainer="mySets"> <EntitySetMapping Name="myTab"> <EntityTypeMapping TypeName="IsTypeOf(myModel.myTab)"> <MappingFragment StoreEntitySet="myTab"> <ScalarProperty Name="aa" ColumnName="a" /> <ScalarProperty Name="bb" ColumnName="b" /> <ScalarProperty Name="cc" ColumnName="d" /> <ScalarProperty Name="dd" ColumnName="c" /> </MappingFragment> </EntityTypeMapping> </EntitySetMapping> </EntityContainerMapping> </Mapping> </edmx:Mappings>
	</edmx:Runtime>
图形设计器的配置部份	<!-- EF Designer content (DO NOT EDIT MANUALLY BELOW HERE) --> <edmx:Designer xmlns="http://schemas.microsoft.com/ado/2007/06/edmx"> <edmx:Connection> <DesignerInfoPropertySet> <DesignerProperty Name="MetadataArtifactProcessing" Value="EmbedInOutputAssembly" /> </DesignerInfoPropertySet> </edmx:Connection> <edmx:Options> <DesignerInfoPropertySet> <DesignerProperty Name="ValidateOnBuild" Value="true" /> </DesignerInfoPropertySet> </edmx:Options> <!-- Diagram content (shape and connector positions) --> <edmx:Diagrams> <Diagram Name="myModel"> <EntityTypeShape EntityType="myModel.myTab" Width="1.5" PointX="0.75" PointY="0.75"Height="1.7" IsExpanded="true" /> </Diagram> </edmx:Diagrams> </edmx:Designer>
	</edmx:Edmx>

Context

public class myContext :ObjectContext

{

public myContext(EntityConnection connection) :

base(connection, "mySets")

{

}

public ObjectQuery<myTab> myTab

{

get

{

if ((this._myTab == null))

{

this._myTab = base.CreateQuery<myTab>("[myTab]");

}

return this._myTab;

}

private ObjectQuery<myTab> _myTab;

public void AddTomyTab(myTab myTab)

{

base.AddObject("myTab", myTab);

}

实体类

[EdmEntityType(NamespaceName = "myModel", Name = "myTab")]

[DataContract(IsReference = true)]

[Serializable()]

public class myTab :EntityObject

{

public static myTab CreatemyTab(string aa, string bb)

{

myTab myTab = new myTab();

myTab.aa = aa;

myTab.bb = bb;

return myTab;

}

private string _aa;

[EdmScalarProperty(EntityKeyProperty = true, IsNullable = false)]

[DataMember()]

public string aa

{

get

{

return this._aa;

}

set

{

this.ReportPropertyChanging("aa");

this._aa = StructuralObject.SetValidValue(value, false);

this.ReportPropertyChanged("aa");

}

private string _bb;

[EdmScalarPropertyAttribute(IsNullable = false)]

[DataMemberAttribute()]

public string bb

{

get

{

return this._bb;

}

set

{

this.ReportPropertyChanging("bb");

this._bb = global::System.Data.Objects.DataClasses.StructuralObject.SetValidValue(value,false);

this.ReportPropertyChanged("bb");

}

private string _cc;

[EdmScalarProperty()]

[DataMember()]

public string cc

{

get

{

return this._cc;

}

set

{

this.ReportPropertyChanging("cc");

this._cc =StructuralObject.SetValidValue(value, true);

this.ReportPropertyChanged("cc");

}

private string _dd;

[EdmScalarProperty()]

[DataMember()]

public string dd

{

get

{

return this._dd;

}

set

{

this.ReportPropertyChanging("dd");

this._dd = StructuralObject.SetValidValue(value, true);

this.ReportPropertyChanged("dd");

}

使用

myContext cn;

EntityConnection econ = new EntityConnection();

string s = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

econ.ConnectionString = s;

cn = new myDate.myContext(econ);

this.dataGridView1.DataSource = cn.myTab;

使用向导创建模型

映射基本规则

1.[概念模型]的[数据类型],[键],[非空]约束要与[存储模型]对应

2.[概念模型]的属性名与[存储模型]的字段名不必一致

3.[存储模型]的字段如果有[键],[非空]约束, [概念模型]必需要有对应的属性与之映射

4. [概念模型]中出现的属性,在[存储模型]中必须要有对应的字段映射

5. [存储模型]的多个字段可以映射到[概念模型]的同一个属性上

加载时, [概念模型]的属性加载[存储模型]的第一个字段值

保存时, [概念模型]的属性会保存到[存储模型]的多个字段上

映射条件

一个字段,如果要作为映射条件,就不能映射到属性上
加载数据时,只会加载符合条件的数据
添加数据时, 映射条件字段不可见, 射条件字段的字直接使用设计时的设定值

继承

1. 要实现继承,要使用映射条件进行筛选

2. [概念模型]与 [子概念模型] 所有的筛选条件不能有相的

3. [子概念模型] 自动得到 [概念模型] 的属性

4. [子概念模型] 中可以没有属性

5. 所的[子概念模型] 的筛选条件将以[Or]的方式影响[概念模型]的筛选,也就是说[概念模型]的记录将包括[子概念模型] 记录

6. [概念模型]与 [子概念模型] 共用同一个 [实体集], [实体集]的数据类型为 ObjectQuery<概念模型>

7. 可以使用类型转换的方式从[实体集]得[子概念模型]的数据

myContext context = new myContext();

ObjectQuery<myTab> a = context.myTabSets;

ObjectQuery<myTabEx1> b = context.myTabSets.OfType<myTabEx1>();

ObjectQuery<myTabEx2> c = context.myTabSets.OfType<myTabEx2>();

多表联合

1. 不要求在数据库中有关系,最好是主键对主键

2. 使用对联的方式,只筛选出有对应键的记录

3. 插入时,会在两个表中同时插入键相同的记录

4. 删除时,会同时在两个表中删除键相同的记录

关联

[(1)—(*)] 关联

1. [(1)—(*)]为主外关系,主键表为(1),外键表为(*)

2. 外键字段不能出现在[概念模型]中

3. 可以在向导中直接跟据数据库中的关系直接生成,也可以在设计[概念模型]时任意添加

4. 关联要绑定到外键表上

5. 要删除主键时,要保证内存中没有对应的外键数据

6. 插入外键数据,可以插入到主键的外键集合,也可创建带主键信息的外键对象后直接插入到Context中

表

设置

操作数据

从主键表访问数据

myContext context = new myContext();

ObjectQuery<tab1> tab1_List = context.tab1;

foreach (tab1 tab1_Entity in tab1_List)

{

Console.WriteLine("{0},{1}", tab1_Entity.a, tab1_Entity.b);

EntityCollection<tab2> tab2_List = tab1_Entity.Nvtab2;

tab2_List.Load(); //加载外键数据

foreach (tab2 tab2_Entity in tab2_List)

{

Console.WriteLine("{0},{1},{2}", tab2_Entity.ID,tab2_Entity.x,tab2_Entity.y);

}

lzm ,456

3 ,5 ,6

4 ,7 ,8

wxd ,123

1 ,1 ,2

2 ,3 ,4

从外键表访问数据

myContext context = new myContext();

ObjectQuery<tab2> tab2_List = context.tab2;

foreach (tab2 tab2_Entity in tab2_List)

{

Console.WriteLine("{0},{1},{2}", tab2_Entity.ID, tab2_Entity.x, tab2_Entity.y);

tab2_Entity.NVtab1Reference.Load(); //加载主键数据

tab1 tab1 = tab2_Entity.NVtab1;

Console.WriteLine("{0},{1}", tab1.a, tab1.b);

}

1 ,1 ,2

wxd ,123

2 ,3 ,4

wxd ,123

3 ,5 ,6

lzm ,456

4 ,7 ,8

lzm ,456

删除主键

myContext context = new myContext();

var v = context.tab1.First(p => p.a == "wxd");

// 要删除主键时,要保证内存中对应的外键数据为空

//v.Nvtab2.Load();

//if (v.Nvtab2.Count != 0)

//{

// List<tab2> list = new List<tab2>();

// foreach (var w in v.Nvtab2)

// {

// list.Add(w);

// }

// foreach (var ww in list)

// {

// context.DeleteObject(ww);

// }

//}

context.DeleteObject(v);

context.SaveChanges();

直接插入外键数据

myContext context = new myContext();

tab2 tab2 = new tab2();

tab2.ID = "101";

tab2.x = "555";

tab2.y = "666";

tab2.Nvtab1 = context.tab1.First(p => p.a == "wxd"); //要有主键信息

context.AddTotab2(tab2);

context.SaveChanges();

通过主键插入外键数据

myContext context = new myContext();

var tab1 = context.tab1.First(p => p.a == "wxd");

//第1条外键记录

tab2 r1 = new tab2();

r1.ID = "103";

r1.x = "r1";

r1.y = "r1";

tab1.Nvtab2.Add(r1);

//第2条外键记录

tab2 r2 = new tab2();

r2.ID = "104";

r2.x = "r1";

r2.y = "r1";

tab1.Nvtab2.Add(r2);

context.SaveChanges();

[(1)—(1)]关联

1. [(1)—(1)]为主主关系,既两个表的主键关联

2. 两个表的地位是平等的

3. 主键字段不能删除

4. 可以在向导中直接跟据数据库中的关系直接生成,也可以在设计[概念模型]时任意添加

5. 关联可绑定到任意一个表上

6. 删除时,要先将关联数据删除

7. 插入时,要有与之关联的数据

表

设置

操作数据

读取

myContext context = new myContext();

ObjectQuery<tab1> tab1_List = context.tab1;

foreach (tab1 tab1_Entity in tab1_List)

{

Console.WriteLine("{0},{1}", tab1_Entity.a, tab1_Entity.b);

tab1_Entity.NVtab3Reference.Load(); //加载关联数据

tab3 tab3 = tab1_Entity.NVtab3;

Console.WriteLine("{0},{1},{2}", tab3.a, tab3.m, tab3.n);

}

lzm ,456

lzm ,mmmm ,nnnn

wxd ,123

wxd ,nnn ,nnn

myContext context = new myContext();

ObjectQuery<tab3> tab3_List = context.tab3;

foreach (tab3 tab3_Entity in tab3_List)

{

Console.WriteLine("{0},{1},{2}", tab3_Entity.a, tab3_Entity.m,tab3_Entity.n );

tab3_Entity.NVtab1Reference.Load(); //加载关联数据

tab1 tab1 = tab3_Entity.NVtab1;

Console.WriteLine("{0},{1}", tab1.a, tab1.b );

}

lzm ,mmmm ,nnnn

lzm ,456

wxd ,nnn ,nnn

wxd ,123

删除

myContext context = new myContext();

var tab3 = context.tab3.First(p => p.a == "wxd");

//-要按顺序

tab3.NVtab1Reference.Load(); // 加载关联数据

context.DeleteObject(tab3.NVtab1); //删除关联数据

context.DeleteObject(tab3); // 删除

context.SaveChanges();

插入

myContext context = new myContext();

tab1 tab1 = new tab1();

tab1.a = "wxwinter";

tab1.b = "789";

//关联

tab1.NVtab3 = new tab3();

tab1.NVtab3.a = "wxwinter";

tab1.NVtab3.m = "mm";

tab1.NVtab3.n = "mm";

context.AddTotab1(tab1);

context.SaveChanges();

[(1)—(0..1)]关联

设计与[(1)—(0..1)]相同.

1. 插入(1)时,可以不插入(0..1)

2. 删除(0..1) 时,可以不删除(1)

3. 插入(0..1)时,需要插入(1)

4. 删除(1) 时, 需要删除(0..1)

[()—()]关联

表

显示中转方式

隐示中转方式

1. 要实现这个关联,要将关联绑定到 [中转表(安排表)]上

2. 所用的[中转表(安排表)]不能以[概念模型]的方式出现

3. 两个表的地位是平等的

4. 添加一端的(*)时,不受另一端(*)约束

5. 可以在添加一端的(*)时,通过[关联集合]将数据也添加到[关联表]与[中转表]中

6. 如果加载关联数据,[中转表]中的关联数据也会被删除.

如果不加载关联数据,将不会删除[中转表]中的关联数据

操作数据

得到数据

myContext context = new myContext();

ObjectQuery<部门表> bList = context.部门表;

foreach (部门表 b in bList)

{

Console.WriteLine("{0},{1}", b.部门, b.部门说明);

b.场地表.Load();

EntityCollection<场地表> cList = b.场地表;

foreach (场地表 c in cList)

{

Console.WriteLine("{0},{1}", c.场地, c.场地说明);

}

丙 ,1

a ,11

b ,22

c ,33

甲 ,2

a ,11

乙 ,3

a ,11

b ,22

myContext context = new myContext();

ObjectQuery<场地表> cList = context.场地表;

foreach (场地表 c in cList)

{

Console.WriteLine("{0},{1}", c.场地, c.场地说明);

c.部门表.Load();

EntityCollection<部门表> bList = c.部门表;

foreach (部门表 b in bList)

{

Console.WriteLine("{0},{1}", b.部门, b.部门说明);

}

a ,11

丙 ,1

甲 ,2

乙 ,3

b ,22

丙 ,1

乙 ,3

c ,33

丙 ,1

删除数据

myContext context = new myContext();

场地表 c = context.场地表.First(p => p.场地 == "a");

//1.如果加载关联数据,[中转表]中的关联数据也会被删除,

//2.如果不加载关联数据,将不会删除[中转表]中的关联数据

//c.部门表.Load(); // <-------[是/否]

context.DeleteObject(c);

context.SaveChanges();

添加数据

myContext context = new myContext();

场地表 c = new 场地表();

c.场地 = "d";

c.场地说明 = "44";

context.AddTo场地表(c);

context.SaveChanges();

同时添加数据到

[源表],

[关联表],

[中转表]

//可以将数据同时添加[源表],[关联表],[中转表]

myContext context = new myContext();

场地表 c = new 场地表();

c.场地 = "e";

c.场地说明 = "55";

c.部门表.Add(new 部门表() { 部门 = "vv", 部门说明 = "vv" });

context.AddTo场地表(c);

context.SaveChanges();

映射存储过程与函数

返回表型存储过程

存储过程

查询

PRSelectDBItem

CREATE PROCEDURE PRSelectDBItem

@v nvarchar(50)

select * from DBItem where ItemID=@v

使用向导生成映射

myContext context = new myContext();

ObjectResult<DBItem> dbitemList= context.PRSelectDBITem("a");

foreach (var r in dbitemList)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

代码实现

public class Context :ObjectContext

{

public Context() : base("name=myContext", "myContext")

{ }

public ObjectResult<DBItem> PRSelectDBITem(string v)

{

return base.ExecuteFunction<DBItem>("PRSelectDBITem", new ObjectParameter("v", v));

}

Context context = new Context();

ObjectResult<DBItem> dbitemList = context.PRSelectDBITem("a");

foreach (var r in dbitemList)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

命令型存储过程

存储过程

插入

PRinsertDBItem

CREATE PROCEDURE PRinsertDBItem

@ItemID nvarchar(50),

@ItemMatter nvarchar(50)

insert into DBItem (ItemID,ItemMatter) values (@ItemID,@ItemMatter)

使用向导生成映射

代码实现

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection();

econ.ConnectionString = econString;

EntityCommand ecmd = new EntityCommand();

ecmd.CommandType = CommandType.Text;

ecmd.Connection = econ;

ecmd.CommandText = "myContext.PRinsertDBItem";

ecmd.CommandType = CommandType.StoredProcedure;

EntityParameter p1 = new EntityParameter("ItemID", System.Data.DbType.String);

p1.Value = "aaa";

EntityParameter p2 = new EntityParameter("ItemMatter", System.Data.DbType.String);

p2.Value = "bbb";

ecmd.Parameters.Add(p1);

ecmd.Parameters.Add(p2);

econ.Open();

ecmd.ExecuteNonQuery();

参数返回值型存储过程

存储过程

算加法

PRadd

CREATE PROCEDURE PRadd

@x int = 0,

@y int = 0,

@s int = 0 output

set @s= @x * @y

使用向导生成映射

代码实现

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection();

econ.ConnectionString = econString;

EntityCommand ecmd = new EntityCommand();

ecmd.CommandType = CommandType.Text;

ecmd.Connection = econ;

ecmd.CommandText = "myContext.PRadd";

ecmd.CommandType = CommandType.StoredProcedure;

EntityParameter p1 = new EntityParameter("x", System.Data.DbType.Int32);

p1.Value = 123;

EntityParameter p2 = new EntityParameter("y", System.Data.DbType.Int32);

p2.Value = 456;

EntityParameter rt = new EntityParameter("s",

System.Data.DbType.Int32,

ParameterDirection.Output,

false,

"",

DataRowVersion.Current,

0);

ecmd.Parameters.Add(p1);

ecmd.Parameters.Add(p2);

ecmd.Parameters.Add(rt);

econ.Open();

ecmd.ExecuteNonQuery();

Console.WriteLine(rt.Value); //579

说明

ObjectContext提供了管理数据的功能

Context操作数据

AddObject 添加实体

将实体添加到集合中,

创建实体时,状态为EntityState.Detached

当调用AddObject将实体添加到Context时,状态为EntityState.Added

myContext context = new myContext();

myTab r = new myTab();

r.ID = 10;

r.a = "wxwinter";

Console.WriteLine(r.EntityState); //print:Detached

context.AddTomyTab(r);

Console.WriteLine(r.EntityState); //print:Added

context.SaveChanges();

myContext context = new myContext();

myTab newrow = new myTab() { a = "wxd", b = "lzm", c = "wxwinter" };

context.AddObject("myTab",newrow);

context.SaveChanges();

DeleteObject 删除实体

将集合中的实体添标记为删除

当调用Context.DeleteObject时,并不是将实体移除集合,而是将实体添标记为EntityState.Deleted ,在下次调用SaveChanges()方法时跟新数据库

myContext context = new myContext();

myTab r = context.myTab.First(p=>p.ID==1);

Console.WriteLine(r.EntityState); //print:Unchanged

context.DeleteObject(r);

Console.WriteLine(r.EntityState); //print:Deleted

context.SaveChanges();

Detach 分离实体

将实体从Context中分离,将状态标记为EntityState.Detached 。

myContext context = new myContext();

myTab r = myTab.CreatemyTab(22);

Console.WriteLine(r.EntityState); //print:Detached

context.AddTomyTab(r);

Console.WriteLine(r.EntityState); //print:Added

context.Detach(r);

Console.WriteLine(r.EntityState); //print: Detached

修改实体

可以直接修在实体对象上修改

当修改在Context中的实体时,会将实体的状态标记为EntityState.Modified

myContext context = new myContext();

myTab r = context.myTab.First(p=>p.ID==1);

Console.WriteLine(r.EntityState); //print:Unchanged

r.a = "wxwinter";

Console.WriteLine(r.EntityState); //print:Modified

context.SaveChanges();

ApplyPropertyChanges 修改实体

使用ApplyPropertyChanges,可以使用不在集合中的实体覆盖到集合中主键对应用实体上,如果内存中没有主键对应的记录,会报错:“ObjectStateManager 不包含具有对“XXX”类型的对象的引用的 ObjectStateEntry。”该方法还有一个特点就是，会拿内存中的对象（新对象）和context中的对象（旧对象）对比，自动生成对应字段修改的Update语句，如果内存中的对象与context中的对象完全相等(每个字段的值都相等),将不生成响应的Update

myContext context = new myContext();

myTab r1 = context.myTab.First(p => p.ID == 1);

myTab nr = myTab.CreatemyTab(1);

nr.a = "wxwinter";

Console.WriteLine(nr.EntityState); //print:Detached

Console.WriteLine(r1.EntityState); //print:Unchanged

context.ApplyPropertyChanges("myTab", nr);

myTab r2 = context.myTab.First(p => p.ID == 1);

Console.WriteLine(nr.EntityState); //print:Detached

Console.WriteLine(r2.EntityState); //print:Modified

context.SaveChanges();

Orders order;
using (NorthwindEntities ne = new NorthwindEntities())
{
    //利用EntityObject.Execute(MergeOption.NoTracking)，等效于使用ObjectContext.Dettach(EntityObject)
    //查询并分离对象
    order = ne.Orders.Execute(MergeOption.NoTracking).Where(v => v.OrderID == 10248).FirstOrDefault();
}
//修改分离的值
order.ShipName = "1111111111111111";
//使用分离的对象 order 更新
using (NorthwindEntities context = new NorthwindEntities())
{
    //将数据载入到context中以便更新
    context.GetObjectByKey(order.EntityKey);
    //使用order 更新 context中的对应对象
    context.ApplyPropertyChanges(order.EntityKey.EntitySetName, order);
    context.SaveChanges();
}

Attach / AttachTo 附加实体

使用Attach方法可将[外部实体]附加到Context集合中

在使用服务器/客户端模式,或要将[实体]从Context集合中分离,修改后要用Context更新回数据库时,可用这种方式

Attach与ApplyPropertyChanges有类似之处,都是将Context集合外的[实体]与Context集合内的[实体]同步.

ApplyPropertyChanges调用时,要求对应的[实体]在内存中,Attach不要求
ApplyPropertyChanges调用后,集合内的实体状态会标记为EntityState.Modified
Attach调用后不会修改合内的实体状态,如要SaveChanges(),要手动标记EntityState.Modified
ApplyPropertyChanges是用[外部实体]全覆盖Context集合中的[实体],
Attach方式,通过SetModifiedProperty()方法,可在调用SaveChanges()时,只修改只定有字段值

myContext context = new myContext();
myTab v = myTab.CreatemyTab(1);
v.EntityKey = context.CreateEntityKey("myTab", v);
v.a = "wxwinter";
context.Attach(v);
//context.AttachTo("myTab", v);
ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(v);
//设置修改
ose.SetModified();
//指定修改的字段名
ose.SetModifiedProperty("a");
context.SaveChanges();

修改前

修改后

CreateEntityKey 创建EntityKey

myContext context = new myContext();

myTab nr = myTab.CreatemyTab(1);

EntityKey ek= context.CreateEntityKey("myTab", nr);

EntityKey

EntityContainerName 属性
EntityKeyValues 集合
EntitySetName 属性
IsTemporary 属性
GetEntitySet(System.Data.Metadata.Edm.MetadataWorkspace) 方法
OnDeserialized(System.Runtime.Serialization.StreamingContext) 方法
OnDeserializing(System.Runtime.Serialization.StreamingContext) 方法

GetObjectByKey/TryGetObjectByKey 通过EntityKey得到实体

myContext context = new myContext();

myTab nr = myTab.CreatemyTab(1);

EntityKey ek= context.CreateEntityKey("myTab", nr);

myTab r = context.GetObjectByKey(ek) as myTab ;

Console.WriteLine("{0},{1},{2},{3}", r.ID, r.a, r.b, r.c);

myContext context = new myContext();

myTab nr = myTab.CreatemyTab(1);

EntityKey ek= context.CreateEntityKey("myTab", nr);
object obj;

if (context.TryGetObjectByKey(ek,out obj))

{

myTab r = obj as myTab;

Console.WriteLine("{0},{1},{2},{3}", r.ID, r.a, r.b, r.c);

}

CreateQuery 创建查询

更多见esql

myContext context = new myContext();

string esql = "SELECT VALUE DBItemList FROM myContext.DBItemList";

// ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql, context);

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine(r.NameID);

}

状态管理

EntityState 状态枚举

EntityState.Added 已通过AddObject方法加到集合中，AcceptChanges 尚未调用。

EntityState.Deleted 已通过 DeleteObject 方法被删除。

EntityState.Detached 已被创建，但不属于任何集合。在以下情况下立即处于此状态：创建之后添加到集合中之前；或从集合中移除之后。

EntityState.Modified 已被修改，AcceptChanges 尚未调用。

EntityState.Unchanged 自上次调用 AcceptChanges 以来尚未更改

Context.ObjectStateManager 管理记录的状态

GetObjectStateEntry 根据实体对象或实体主键得到状态实体

实体必须在当前连接对象 context 中否则无法获取实体状态会引发：
ObjectStateManager 不包含具有对“ context ”类型的对象的引用的 ObjectStateEntry
也就是该方法无法获取已分离的实体对象状态

ObjectStateEntry = GetObjectStateEntry(实体对像/EntityKey)

得到所指定的[实体对像]或EntityKey的 ObjectStateEntry

myContext context = new myContext();

myTab r = myTab.CreatemyTab(22);

context.AddTomyTab(r);

// ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r.EntityKey);

Console.WriteLine(ose.State); //print:Added

TryGetObjectStateEntry 根据实体对象或实体主键得到状态实体

bool = TryGetObjectStateEntry(实体对像/EntityKey,out ObjectStateEntry)

得到所指定的[实体对像]或EntityKey的 ObjectStateEntry

myContext context = new myContext();

myTab r = myTab.CreatemyTab(22);

context.AddTomyTab(r);

ObjectStateEntry ose;

if( context.ObjectStateManager.TryGetObjectStateEntry(r,out ose))

{

Console.WriteLine(ose.State); //print:Added

}

GetObjectStateEntries 根据状态类型得到状态实体集合

IEnumerable<ObjectStateEntry> = GetObjectStateEntries(EntityState枚举)

返回IEnumerable<ObjectStateEntry>,得到EntityState枚举所指定的某种状态的列表

myContext context = new myContext();

myTab r = myTab.CreatemyTab(22);

context.AddTomyTab(r);

IEnumerable<ObjectStateEntry> oseList = context.ObjectStateManager.GetObjectStateEntries(EntityState.Added);

foreach (ObjectStateEntry v in oseList)

{

Console.WriteLine("{0},{1},{2}", v.State, v.CurrentValues["ID"], v.EntitySet.Name);

}

//print:Added,22,myTab

ObjectStateManagerChanged 事件

CollectionChangeEventHandler(object sender, CollectionChangeEventArgs e)

e.Action : 集合操作行为

System.ComponentModel.CollectionChangeAction.Add

System.ComponentModel.CollectionChangeAction.Refresh

System.ComponentModel.CollectionChangeAction.Remove

e.Element : 操作的实体对象

void ObjectStateManager_ObjectStateManagerChanged(object sender, CollectionChangeEventArgse)

{

Console.WriteLine(e.Action);
myTab v = e.Element as myTab;

Console.WriteLine("{0}",v.ID);

}

//===================================

myContext context = new myContext();

context.ObjectStateManager.ObjectStateManagerChanged+=newCollectionChangeEventHandler(ObjectStateManager_ObjectStateManagerChanged);

myTab r = myTab.CreatemyTab(22);

context.AddTomyTab(r);

*print:

Add

ObjectStateEntry 对象

基本属性

IsRelationship 属性
Entity 属性
EntityKey 属性
EntitySet 属性

State 状态属性

EntityState 枚举

myContext context = new myContext();

myTab r = myTab.CreatemyTab(22);

context.AddTomyTab(r);

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

Console.WriteLine(ose.State); //print:Added

CurrentValues 当前值

处于 deleted 或 detached 状态的对象没有当前值。

myContext context = new myContext();

myTab r = new myTab() { ID = 22, a = "wxwinter" };

context.AddTomyTab(r);

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

Console.WriteLine("{0},{1}",ose.CurrentValues["ID"],ose.CurrentValues["a"]);

//print: 22,wxwinter

OriginalValues 原始值

处于 added 或 detached 状态的对象没有原始值

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);

r.a = "wxwinter";

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

Console.WriteLine(ose.State);

Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);

Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

* print:

Modified

CurrentValues :1,wxwinter

OriginalValues:1,aa

GetModifiedProperties 得到被修改的属性

返回IEnumerable<string>

得到被修改的属性集合

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);

r.a = "wxwinter";

r.b = "wxd";

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

IEnumerable<string> list = ose.GetModifiedProperties();

foreach (string pr in list)

{

Console.WriteLine(pr);

}

* print:

SetModified,SetModifiedProperty 标记为修改

SetModified() 方法将记录标记为 EntityState.Modified

只是这样,调用Context.SaveChanges方法是无法保存修改到数据库中的,Context.SaveChanges方法要查找被修改过的属性,

可用SetModifiedProperty方法标记被修改过的属性

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);

r.a = "wxwinter";

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);
ose.AcceptChanges();

Console.WriteLine(ose.State);

Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);

Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

* print:

Unchanged

CurrentValues :1,wxwinter

OriginalValues:1,wxwinter

ose.SetModified();

ose.SetModifiedProperty("a");

Console.WriteLine(ose.State);

Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);

Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

* print:

Modified

CurrentValues :1,wxwinter

OriginalValues:1,wxwinter

context.SaveChanges();

Delete 标记为删除

标记为EntityState.Deleted

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

ose.Delete();

Console.WriteLine(ose.State); //print: Detached

Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

//print:OriginalValues:1,wxwinter

用 context.DeleteObject方法的效果与上例一样

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);
ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r);
context.DeleteObject(r);
Console.WriteLine(ose.State); //print: Detached
Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

//print:OriginalValues:1,wxwinter

AcceptChanges 方法

将记录的状态置为EntityState.Unchanged

用[CurrentValues 当前值]替换[OriginalValues 原始值],

使用[ Context.AcceptAllChanges 方法]也有同样效果

注意:状态为[EntityState.Deleted ]的记录,会被[Detach]

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);
r.a = "wxwinter";

context.AcceptAllChanges();
ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

ose.AcceptChanges();

Console.WriteLine(ose.State);

Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);

Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

* print:

Unchanged

CurrentValues :1,wxwinter

OriginalValues:1,wxwinter

当调用AcceptChanges时,如果对像处于[EntityState.Deleted ],会将对象移除集合,这时对像的状态为[EntityState.Detached ]

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

ose.Delete();

ose.AcceptChanges();

Console.WriteLine(ose.State); //print: Detached

保存修改到数据库

Context.SaveChanges 方法

如果集合中有状态为EntityState.Added的记录,用[CurrentValues 当前值]添加到数据库中

如果集合中有状态为EntityState.Deleted的记录,从数据库是删除与之对应的数据库记录

如果集合中有状态为EntityState.Modified的记录,用[OriginalValues 原始值]与对应的数据库记录比效,查看并发, 用[CurrentValues 当前值]更新与之对应的数据库记录

SaveChanges(true)	将数据保存到数据库后将所有记录状态标记为EntityState.Unchanged ,(调用Context.AcceptAllChanges )
SaveChanges(true)	myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r); context.SaveChanges(true); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Unchanged CurrentValues :1,wxwinter OriginalValues:1,wxwinter */
SaveChanges()	与SaveChanges(true)相同
SaveChanges(false)	将数据保存到数据库, 但并不改变记录状态
SaveChanges(false)	myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r); context.SaveChanges(false); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Modified CurrentValues :1,wxwinter OriginalValues:1,aa */

Context.SavingChanges 事件

myContext context = new myContext();

context.SavingChanges+=new EventHandler(context_SavingChanges);

myTab r = context.myTab.First(p => p.ID == 1);
r.a = "wxwinter";
context.SaveChanges();

void context_SavingChanges(object sender, EventArgs e)

{

myContext context = sender as myContext;

Console.WriteLine(context.DefaultContainerName);

}

Context.AcceptAllChanges 方法

将所有记录的状态置为EntityState.Unchanged

用[CurrentValues 当前值]替换[OriginalValues 原始值]

效果与对所在记录的ObjectStateEntry上调用AcceptAllChanges一样

注意:状态为[EntityState.Deleted ]的记录,会被[Detach]

myContext context = new myContext();

myTab r = context.myTab.First(p => p.ID == 1);

r.a = "wxwinter";

context.AcceptAllChanges();

ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r);

Console.WriteLine(ose.State);

Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);

Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

* print:

Unchanged

CurrentValues :1,wxwinter

OriginalValues:1,wxwinter

连接属性

Context.DefaultContainerName 属性

Context.Connection 属性

Context.CommandTimeout 属性

Context.MetadataWorkspace

数据刷新与并发

EF提供了两种并发冲突处理方式：放任不管方式和开放式并发。默认采用放任不管的方式处理。

如果要使用开放式并发，必须设置相应属性上的[并发模式]值[Fixed]

后修改数据的ObjectContext缓存了旧版本的数据时,当提交修改后系统就会抛出"OptimisticConcurrencyException"（开放式并发异常）。

当程序捕获到异常以后，可以使用ObjectContext的Refresh方法对异常采取处理。

缓存数据不会自动更新

公共

myContext context1 = new myContext();

myContext context2 = new myContext();

查询

foreach (var r in context1.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

a,this is a

b,this is b

c,this is c

---------------------

a,this is a

b,this is b

c,this is c

修改

DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");

dbitem1.ItemMatter = "hello";

context1.SaveChanges();

再查询

foreach (var r in context1.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

a,hello

b,this is b

c,this is c

---------------------

a,this is a

b,this is b

c,this is c

[并发模式]值为[Fixed]的并发异常

注意,只有后修改数据的ObjectContext缓存了旧版本的数据时,长会产生异常

DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");

dbitem1.ItemMatter = "hello";

context1.SaveChanges();

DBItem dbitem2 = context2.DBItem.First(p => p.ItemID == "a");

dbitem2.ItemMatter = "wxwinter";

context2.SaveChanges();

ObjectContext.Refresh()

Refresh的第一个参数RefreshMode枚举,RefreshMode.StoreWins,RefreshMode.ClientWins

StoreWins

StoreWins : Refresh以后，用数据库的值回写,当前的修改值被放弃

公共

myContext context1 = new myContext();

myContext context2 = new myContext();

查询

foreach (var r in context1.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

a,this is a

b,this is b

c,this is c

---------------------

a,this is a

b,this is b

c,this is c

修改

DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");

dbitem1.ItemMatter = "hello";

context1.SaveChanges();

DBItem dbitem2 = context2.DBItem.First(p => p.ItemID == "a");

dbitem2.ItemMatter = "wxwinter";

try

{

context2.SaveChanges();

}

catch

{

context2.Refresh( RefreshMode.StoreWins , dbitem2);

}

在System.Data.OptimisticConcurrencyException 中第一次偶然出现的"System.Data.Entity.dll"类型的异常

再查询

foreach (var r in context1.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

a,hello

b,this is b

c,this is c

---------------------

a,hello

b,this is b

c,this is c

ClientWins

StoreWins: Refresh以后，当前的修改值仍存在,只是告诉ObjectContext知到的并发问题了,这时再调用 ObjectContext.SaveChanges()时,ObjectContext就不会报[开放式并发异常]

DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");

dbitem1.ItemMatter = "hello";

context1.SaveChanges();

DBItem dbitem2 = context2.DBItem.First(p => p.ItemID == "a");

dbitem2.ItemMatter = "wxwinter";

try

{

context2.SaveChanges();

}

catch

{

context2.Refresh(RefreshMode.ClientWins, dbitem2);

context2.SaveChanges();

}

也可以先Refresh()再SaveChanges(),而不用异常捕获

DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");

dbitem1.ItemMatter = "hello";

context1.SaveChanges();

DBItem dbitem2 = context2.DBItem.First(p => p.ItemID == "a");

dbitem2.ItemMatter = "wxwinter";

context2.Refresh(RefreshMode.ClientWins, dbitem2);

context2.SaveChanges();

事务处理

同一SubmitChanges 会做默认的事务处理

下例由于ItemID主键冲突,两条数据都不会被插入

myContext context1 = new myContext();

DBItem item1 = new DBItem();

item1.ItemID = "w";

item1.ItemMatter = "wxwinter";

context1.AddObject("DBItem", item1);

DBItem item2 = new DBItem();

item2.ItemID = "w";

item2.ItemMatter = "wxd";

context1.AddObject("DBItem", item2);

context1.SaveChanges();

不同SubmitChanges 不会做事务处理

下例由于ItemID主键冲突,后一条数据都不会被插入

myContext context1 = new myContext();

DBItem item1 = new DBItem();

item1.ItemID = "w";

item1.ItemMatter = "wxwinter";

context1.AddObject("DBItem", item1);

context1.SaveChanges();

myContext context2 = new myContext();

DBItem item2 = new DBItem();

item2.ItemID = "w";

item2.ItemMatter = "wxd";

context2.AddObject("DBItem", item2);

context2.SaveChanges();

System.Data.Common.DbTransaction

下例由于ItemID主键冲突,两条数据都不会被插入

myContext context1 = new myContext();

DBItem item1 = new DBItem();

item1.ItemID = "w";

item1.ItemMatter = "wxwinter";

context1.AddObject("DBItem", item1);

if (context1.Connection.State != ConnectionState.Open)

{

context1.Connection.Open();

}

System.Data.Common.DbTransaction tran = context1.Connection.BeginTransaction();

context1.SaveChanges();

try

{

DBItem item2 = new DBItem();

item2.ItemID = "w";

item2.ItemMatter = "wxd";

context1.AddObject("DBItem", item2);

context1.SaveChanges();

tran.Commit();

}

catch

{

tran.Rollback();

}

死锁(两个Context使用DbTransaction)

myContext context1 = new myContext();

DBItem item1 = new DBItem();

item1.ItemID = "w";

item1.ItemMatter = "wxwinter";

context1.AddObject("DBItem", item1);

if (context1.Connection.State != ConnectionState.Open)

{

context1.Connection.Open();

}

System.Data.Common.DbTransaction tran = context1.Connection.BeginTransaction();

context1.SaveChanges();

try

{

myContext context2 = new myContext();

DBItem item2 = new DBItem();

item2.ItemID = "w";

item2.ItemMatter = "wxd";

context2.AddObject("DBItem", item2);

context2.SaveChanges();

tran.Commit();

}

catch

{

tran.Rollback();

}

TransactionScope 事务(两个Context)

System.Transactions.TransactionScope

可解决[死锁(两个Context使用DbTransaction)]

下例由于ItemID主键冲突,两条数据都不会被插入

using (System.Transactions.TransactionScope tc = new TransactionScope())

{

try

{

myContext context1 = new myContext();

DBItem item1 = new DBItem();

item1.ItemID = "w";

item1.ItemMatter = "wxwinter";

context1.AddObject("DBItem", item1);

context1.SaveChanges();

myContext context2 = new myContext();

DBItem item2 = new DBItem();

item2.ItemID = "w";

item2.ItemMatter = "wxd";

context2.AddObject("DBItem", item2);

context2.SaveChanges();

tc.Complete();

}

catch

{

}

ObjectQuery<T>数据加载方式

1. ObjectQuery<T> 提供了一个管理[实体对像]集合
2. ObjectQuery<T>继承System.Data.Objects.ObjectQuery, ObjectQuery对ObjectContext进行了封装，
3.可以通过ObjectContext.CreateQuery<T>("esql")的方式创建ObjectQuery<T>
4.可以通过new ObjectQuery<T>(ObjectContext,"esql")的方式创建ObjectQuery<T>,跟据SQL字串的不同，会得到具体的ObjectQuery<值类型>，或ObjectQuery<DbDataRecord>或ObjectQuery<实体>

访问方式

Context.CreateQuery<T>()

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);
ObjectContext context = new ObjectContext(econ);
context.DefaultContainerName = "myContext";
ObjectQuery<DBItem> queryTab = context.CreateQuery<DBItem>("DBItem");

foreach (var r in queryTab)

{

System.Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);

}

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);

ObjectContext context = new ObjectContext(econ);

ObjectQuery<DBItem> queryTab = context.CreateQuery<DBItem>("select value it from myContext.DBItem as it where it.ItemID='a'");

foreach (var r in queryTab)

{

System.Console.WriteLine("{0},{1}",r.ItemID,r.ItemMatter);

}

ObjectQuery<DbDataRecord>

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);

ObjectContext context = new ObjectContext(econ);

ObjectQuery<DbDataRecord> queryTab = new ObjectQuery<DbDataRecord>("select it.ItemID,it.ItemMatter from myContext.DBItem as it", context）

foreach (var r in queryTab)

{

System.Console.WriteLine("{0},{1}",r[0].ToString(),r[1].ToString());

}

ObjectQuery<简单类型>

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);

ObjectContext context = new ObjectContext(econ);

ObjectQuery<int> queryTab = new ObjectQuery<int>("select value Count(it.ItemID) from myContext.DBItem as it", context);

foreach (var r in queryTab)

{

System.Console.WriteLine("个数:{0}", r.ToString() );

}

Execute方法与ObjectResult

Execute方法

string econString = @"

metadata=res://*/myModel.csdl

|res://*/myModel.ssdl

|res://*/myModel.msl

;

provider=System.Data.SqlClient;

provider connection string=""

Data Source=.;

Initial Catalog=LingTestDB;

Integrated Security=True;

MultipleActiveResultSets=True;

EntityConnection econ = new EntityConnection(econString);

ObjectContext context = new ObjectContext(econ);

context.DefaultContainerName = "myContext";

ObjectQuery<DBItem> queryTab = context.CreateQuery<DBItem>("DBItem");

ObjectResult<DBItem> resultTab = queryTab.Execute(MergeOption.NoTracking);

foreach (var r in resultTab)

{

System.Console.WriteLine("{0},{1}",r.ItemID,r.ItemMatter);

}

ObjectResult<T> 结果集

ObjectQuery<T>.Execute()方法返回ObjectResult<T>对象

类型转换

OfType(TResultType)

ObjectQuery<TResultType> OfType<TResultType>();

myContext context = new myContext();

ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

Linq方法

All

判断集合中是否所有元素都满足某一条件

myContext context = new myContext();

bool b= context.DBItemList.All(p => p.ItemValue >= 0);

SELECT

CASE WHEN ( NOT EXISTS (SELECT

cast(1 as bit) AS [C1]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE ( NOT ([Extent1].[ItemValue] >= 1)) OR (CASE WHEN ([Extent1].[ItemValue] >= 0) THEN cast(1 as bit) WHEN ( NOT([Extent1].[ItemValue] >= 0)) THEN cast(0 as bit) END IS NULL)

)) THEN cast(1 as bit) WHEN ( EXISTS (SELECT

cast(1 as bit) AS [C1]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE ( NOT ([Extent2].[ItemValue] >= 0)) OR (CASE WHEN ([Extent2].[ItemValue] >= 0) THEN cast(1 as bit) WHEN ( NOT([Extent2].[ItemValue] >= 0)) THEN cast(0 as bit) END IS NULL)

)) THEN cast(0 as bit) END AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

Any

判断集合中是否有元素满足某一条件

myContext context = new myContext();

bool b = context.DBItemList.Any(p => p.ItemValue == 4);

SELECT

CASE WHEN ( EXISTS (SELECT

cast(1 as bit) AS [C1]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE 4 = [Extent1].[ItemValue]

)) THEN cast(1 as bit) WHEN ( NOT EXISTS (SELECT

cast(1 as bit) AS [C1]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE 4 = [Extent2].[ItemValue]

)) THEN cast(0 as bit) END AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

Take

获取集合的前n个元素

myContext context = new myContext();

IQueryable<DBItemList> list = context.DBItemList.Take(3);

SELECT TOP (3)

[c].[AutoId] AS [AutoId],

[c].[NameID] AS [NameID],

[c].[ItemID] AS [ItemID],

[c].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [c]

Skip

跳过集合的前n个元素,

Linq To Entity 要求必须先OrderBy

myContext context = new myContext();

IQueryable<DBItemList> list = context.DBItemList.OrderBy(p=>p.ItemValue).Skip(5);

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM ( SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS [NameID], [Extent1].[ItemID] AS [ItemID],[Extent1].[ItemValue] AS [ItemValue], row_number() OVER (ORDER BY [Extent1].[ItemValue] ASC) AS [row_number]

FROM [dbo].[DBItemList] AS [Extent1]

) AS [Extent1]

WHERE [Extent1].[row_number] > 5

ORDER BY [Extent1].[ItemValue] ASC

First

集合的第一个元素,集合中没有会报错,

myContext context = new myContext();

DBItemList f1 = context.DBItemList.First();

DBItemList fi = context.DBItemList.First(p => p.ItemValue == 5);

SELECT TOP (1)

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE 5 = [Extent1].[ItemValue]

FirstOrDefault

集合中的第一个元素,没有则返回类型默认值,对象型默认值为null

myContext context = new myContext();

DBItemList fi = context.DBItemList.FirstOrDefault(p => p.ItemValue ==5);

if (fi != null)

{

Console.WriteLine(fi.ItemValue);

}

Where

用LinqExpressions为条件进行查询

myContext context = new myContext();

IQueryable<DBItemList> list= context.DBItemList.Where(p => p.ItemValue == 5);

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE 5 = [Extent1].[ItemValue]

Distinct

过滤集合中的相同项

ObjectQuery<T> Distinct()

myContext context = new myContext();

ObjectQuery<DbDataRecord> list = context.DBItemList.Select("it.ItemValue");

ObjectQuery<DbDataRecord> dlist= list.Distinct();

SELECT

[Distinct1].[C1] AS [C1],

[Distinct1].[ItemValue] AS [ItemValue]

FROM ( SELECT DISTINCT

[Extent1].[ItemValue] AS [ItemValue],

1 AS [C1]

FROM [dbo].[DBItemList] AS [Extent1]

) AS [Distinct1]

OrderBy,OrderByDescending

排序升,排序降

myContext context = new myContext();

IQueryable<DBItemList> list = context.DBItemList.OrderBy(p=>p.ItemValue);

IQueryable<DBItemList> list = context.DBItemList.OrderByDescending(p=>p.ItemValue);

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

ORDER BY [Extent1].[ItemValue] ASC

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

ORDER BY [Extent1].[ItemValue] DESC

ThenBy,ThenByDescending

ThenBy,ThenByDescending 方法必须跟在 OrderBy 方法或对 ThenBy 方法的另一次调用之后

当用OrderBy,OrderByDescending指定主排序字段后,可用ThenBy呀ThenByDescending指定次排序字段

myContext context = new myContext();

IQueryable<DBItemList> query = context.DBItemList.OrderBy(p=>p.ItemValue).ThenByDescending(p => p.ItemID);

foreach (var r in query)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

ORDER BY [Extent1].[ItemValue] ASC, [Extent1].[ItemID] DESC

Average,Sum

平均值,求和

myContext context = new myContext();

double d = context.DBItemList.Average(p => p.ItemValue);

double s = context.DBItemList.Sum(p => p.ItemValue);

SELECT

[GroupBy1].[A1] AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

LEFT OUTER JOIN (SELECT

AVG( CAST( [Extent1].[ItemValue] AS float)) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1] ) AS [GroupBy1] ON 1 = 1

SELECT

[GroupBy1].[A1] AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

LEFT OUTER JOIN (SELECT

SUM([Extent1].[ItemValue]) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1] ) AS [GroupBy1] ON 1 = 1

Max,Min

集合最大值，最小值

myContext context = new myContext();

var mx = context.DBItemList.Max(p => p.ItemValue);

var mi = context.DBItemList.Min(p => p.ItemValue);

SELECT

[GroupBy1].[A1] AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

LEFT OUTER JOIN (SELECT

MAX([Extent1].[ItemValue]) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1] ) AS [GroupBy1] ON 1 = 1

SELECT

[GroupBy1].[A1] AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

LEFT OUTER JOIN (SELECT

MIN([Extent1].[ItemValue]) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1] ) AS [GroupBy1] ON 1 = 1

Count,LongCount

集合中的元素个数

myContext context = new myContext();

int n = context.DBItemList.Count();

int ni = context.DBItemList.Count(p => p.ItemValue == 5);

long ln = context.DBItemList.LongCount();

SELECT

[GroupBy1].[A1] AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

LEFT OUTER JOIN (SELECT

COUNT(cast(1 as bit)) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE 5 = [Extent1].[ItemValue] ) AS [GroupBy1] ON 1 = 1

Concat

连接不同集合，不会自动过滤相同项,两个集合可以不是同一个Context

myContext context1 = new myContext();

myContext context2 = new myContext();

IQueryable<DBItemList> list1 = context1.DBItemList.Where(p => p.ItemValue == 1);

IQueryable<DBItemList> list2 = context1.DBItemList.Where(p => p.ItemValue == 2);

IQueryable<DBItemList> list = list1.Concat(list2);

SELECT

[UnionAll1].[AutoId] AS [C1],

[UnionAll1].[NameID] AS [C2],

[UnionAll1].[ItemID] AS [C3],

[UnionAll1].[ItemValue] AS [C4]

FROM (SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE 1 = [Extent1].[ItemValue]

UNION ALL

SELECT

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID],

[Extent2].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE 2 = [Extent2].[ItemValue]) AS [UnionAll1]

Union

连接不同集合，自动过滤相同项,两个集合要是同一个Context

ObjectQuery<T> Union(ObjectQuery<T> query)

IQueryable<T> Union( IQueryable<T> query)

IQueryable<T> Uniont( IQueryable<T> query,IEqualityComparer<T>)

myContext context1 = new myContext();

IQueryable<DBItemList> query1 = context1.DBItemList.Where(p => p.ItemID == "c" || p.ItemID == "b");

IQueryable<DBItemList> query2 = context1.DBItemList.Where(p => p.ItemID == "c" || p.ItemID == "a");

IQueryable<DBItemList> v = query2.Union(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

myContext context1 = new myContext();

ObjectQuery<DBItemList> query1 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' ");

ObjectQuery<DBItemList> query2 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ");

ObjectQuery<DBItemList> v = query2.Union(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[Distinct1].[C1] AS [C1],

[Distinct1].[C2] AS [C2],

[Distinct1].[C3] AS [C3],

[Distinct1].[C4] AS [C4]

FROM ( SELECT DISTINCT

[UnionAll1].[AutoId] AS [C1],

[UnionAll1].[NameID] AS [C2],

[UnionAll1].[ItemID] AS [C3],

[UnionAll1].[ItemValue] AS [C4]

FROM (SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE (N'c' = [Extent1].[ItemID]) OR (N'a' = [Extent1].[ItemID])

UNION ALL

SELECT

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID],

[Extent2].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE (N'c' = [Extent2].[ItemID]) OR (N'b' = [Extent2].[ItemID])) AS [UnionAll1]

) AS [Distinct1]

UnionAll

两个集合的相同项都会返回,两个集合要是同一个Context

ObjectQuery<T> UnionAll(ObjectQuery<T> query);

myContext context1 = new myContext();

ObjectQuery<DBItemList> query1 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' ");

ObjectQuery<DBItemList> query2 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ");

ObjectQuery<DBItemList> v = query2.UnionAll(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[UnionAll1].[AutoId] AS [C1],

[UnionAll1].[NameID] AS [C2],

[UnionAll1].[ItemID] AS [C3],

[UnionAll1].[ItemValue] AS [C4]

FROM (SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE ([Extent1].[ItemID] = 'c') OR ([Extent1].[ItemID] = 'a')

UNION ALL

SELECT

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID],

[Extent2].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE ([Extent2].[ItemID] = 'c') OR ([Extent2].[ItemID] = 'b')) AS [UnionAll1]

Except

从某集合中删除其与另一个集合中相同的项,两个集合要是同一个Context

ObjectQuery<T> Except(ObjectQuery<T> query)

IQueryable<T> Except( IQueryable<T> query)

IQueryable<T> Except( IQueryable<T> query,IEqualityComparer<T>)

myContext context1 = new myContext();

IQueryable<DBItemList> query1 = context1.DBItemList.Where(p => p.ItemID == "c" || p.ItemID == "b");

IQueryable<DBItemList> query2 = context1.DBItemList.Where(p => p.ItemID == "c" || p.ItemID == "a");

IQueryable<DBItemList> v = query2.Except(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

myContext context1 = new myContext();

ObjectQuery<DBItemList> query1 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' ");

ObjectQuery<DBItemList> query2 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ");

ObjectQuery<DBItemList> v = query2.Except(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[Except1].[AutoId] AS [C1],

[Except1].[NameID] AS [C2],

[Except1].[ItemID] AS [C3],

[Except1].[ItemValue] AS [C4]

FROM (SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE (N'c' = [Extent1].[ItemID]) OR (N'a' = [Extent1].[ItemID])

EXCEPT

SELECT

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID],

[Extent2].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE (N'c' = [Extent2].[ItemID]) OR (N'b' = [Extent2].[ItemID])) AS [Except1]

Intersect

获取不同集合的相同项（交集）,两个集合要是同一个Context

ObjectQuery<T> Intersect(ObjectQuery<T> query)

IQueryable<T> Intersect( IQueryable<T> query)

IQueryable<T> Intersect( IQueryable<T> query,IEqualityComparer<T>)

myContext context1 = new myContext();

IQueryable<DBItemList> query1 = context1.DBItemList.Where(p => p.ItemID == "c" || p.ItemID == "b");

IQueryable<DBItemList> query2 = context1.DBItemList.Where(p => p.ItemID == "c" || p.ItemID == "a");

IQueryable<DBItemList> v = query2.Intersect(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

myContext context1 = new myContext();

ObjectQuery<DBItemList> query1 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' ");

ObjectQuery<DBItemList> query2 = context1.CreateQuery<DBItemList>("select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ");

ObjectQuery<DBItemList> v = query2.Intersect(query1);

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[Intersect1].[AutoId] AS [C1],

[Intersect1].[NameID] AS [C2],

[Intersect1].[ItemID] AS [C3],

[Intersect1].[ItemValue] AS [C4]

FROM (SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE (N'c' = [Extent1].[ItemID]) OR (N'a' = [Extent1].[ItemID])

INTERSECT

SELECT

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID],

[Extent2].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE (N'c' = [Extent2].[ItemID]) OR (N'b' = [Extent2].[ItemID])) AS [Intersect1]

Select

射影

myContext context = new myContext();

var list = context.DBItemList.Select(p => new {a= p.ItemValue,p.NameID });

SELECT

1 AS [C1],

[Extent1].[ItemValue] AS [ItemValue],

[Extent1].[NameID] AS [NameID]

FROM [dbo].[DBItemList] AS [Extent1]

GroupBy

分组,该方法分组结果集合

System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TElement>>

myContext context = new myContext();

var query = context.DBItemList.GroupBy(p => p.ItemID);

foreach (var g in query)

{

Console.WriteLine(g.Key);

foreach (var r in g)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

23,a,n01,4

24,a,n01,5

25,a,n02,2

26,a,n02,3

27,a,n02,6

28,a,n03,3

11,b,n03,5

14,b,n01,2

16,b,n01,1

5,c,n01,4

7,c,n01,5

9,c,n02,2

10,c,n02,3

12,c,n02,6

17,c,n03,3

SELECT

[Project2].[ItemID] AS [ItemID],

[Project2].[C1] AS [C1],

[Project2].[C2] AS [C2],

[Project2].[AutoId] AS [AutoId],

[Project2].[NameID] AS [NameID],

[Project2].[ItemID1] AS [ItemID1],

[Project2].[ItemValue] AS [ItemValue]

FROM ( SELECT

[Distinct1].[ItemID] AS [ItemID],

1 AS [C1],

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID1],

[Extent2].[ItemValue] AS [ItemValue],

CASE WHEN ([Extent2].[AutoId] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C2]

FROM (SELECT DISTINCT

[Extent1].[ItemID] AS [ItemID]

FROM [dbo].[DBItemList] AS [Extent1] ) AS [Distinct1]

LEFT OUTER JOIN [dbo].[DBItemList] AS [Extent2] ON ([Extent2].[ItemID] = [Distinct1].[ItemID]) OR (([Extent2].[ItemID] ISNULL) AND ([Distinct1].[ItemID] IS NULL))

) AS [Project2]

ORDER BY [Project2].[ItemID] ASC, [Project2].[C2] ASC

Join

联合查询

myContext context1 = new myContext();

ObjectQuery<DBItem> query1 = context1.DBItem;

ObjectQuery<DBItemList> query2 = context1.DBItemList;

var v = query1.Join(query2, temp1 => temp1.ItemID, temp2 => temp2.ItemID, (temp1, temp2) => new { temp1.ItemID, temp1.ItemMatter, temp2.ItemValue, temp2.AutoId, temp2.NameID });

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3},{4}", r.AutoId, r.ItemID, r.NameID, r.ItemValue,r.ItemMatter);

}

myContext context1 = new myContext();

ObjectQuery<DBItem> query1 = context1.DBItem;

ObjectQuery<DBItemList> query2 = context1.DBItemList;

var v = from temp1 in query1 join temp2 in query2 on temp1.ItemID equals temp2.ItemID

select new { temp1.ItemID, temp1.ItemMatter, temp2.ItemValue, temp2.AutoId,temp2.NameID };

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2},{3},{4}", r.AutoId, r.ItemID, r.NameID, r.ItemValue,r.ItemMatter);

}

5,c,n01,4,this is c

7,c,n01,5,this is c

9,c,n02,2,this is c

10,c,n02,3,this is c

11,b,n03,5,this is b

12,c,n02,6,this is c

14,b,n01,2,this is b

16,b,n01,1,this is b

17,c,n03,3,this is c

23,a,n01,4,this is a

24,a,n01,5,this is a

25,a,n02,2,this is a

26,a,n02,3,this is a

27,a,n02,6,this is a

28,a,n03,3,this is a

SELECT

1 AS [C1],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemMatter] AS [ItemMatter],

[Extent2].[ItemValue] AS [ItemValue],

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID]

FROM [dbo].[DBItem] AS [Extent1]

INNER JOIN [dbo].[DBItemList] AS [Extent2] ON ([Extent1].[ItemID] = [Extent2].[ItemID]) OR (([Extent1].[ItemID] IS NULL) AND([Extent2].[ItemID] IS NULL))

GroupJoin

myContext context1 = new myContext();

ObjectQuery<DBItem> query1 = context1.DBItem;

ObjectQuery<DBItemList> query2 = context1.DBItemList;

var v = query1.GroupJoin(query2, temp1 => temp1.ItemID, temp2 => temp2.ItemID, (temp1, temp2) => new { temp1.ItemID, temp1.ItemMatter, 个数 = temp2.Count() });

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2}", r.ItemID, r.ItemMatter,r.个数);

}

myContext context1 = new myContext();

ObjectQuery<DBItem> query1 = context1.DBItem;

ObjectQuery<DBItemList> query2 = context1.DBItemList;

var v = from temp1 in query1

join temp2 in query2 on temp1.ItemID equals temp2.ItemID

into newtab

select new { temp1.ItemID, temp1.ItemMatter, 个数 = newtab.Count() };

foreach (var r in v)

{

Console.WriteLine("{0},{1},{2}", r.ItemID, r.ItemMatter,r.个数);

}

a,this is a,6

b,this is b,3

c,this is c,6

SELECT

1 AS [C1],

[Project1].[ItemID] AS [ItemID],

[Project1].[ItemMatter] AS [ItemMatter],

[Project1].[C1] AS [C2]

FROM ( SELECT

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemMatter] AS [ItemMatter],

(SELECT

COUNT(cast(1 as bit)) AS [A1]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE ([Extent1].[ItemID] = [Extent2].[ItemID]) OR (([Extent1].[ItemID] IS NULL) AND ([Extent2].[ItemID] IS NULL)))AS [C1]

FROM [dbo].[DBItem] AS [Extent1]

) AS [Project1]

无效的Linq方法

可将ObjectQuery<T>转换为List<T>后使用 List的对应方法

Aggregate

据输入的表达式获取一个聚合值

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

DBItemList r = list.Aggregate((x, y) => new DBItemList() { ItemValue = x.ItemValue + y.ItemValue });

Console.WriteLine("ItemValue合计为:{0}", r.ItemValue);

//print: ItemValue合计为:54

TakeWhile

条件第一次不成立就跳出循环

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

IEnumerable<DBItemList> v = list.TakeWhile(p => p.ItemValue >= 2);

foreach (var r in v)

{

Console.WriteLine(r.ItemValue);

}

//print

SkipWhile

条件第一次不成立就失效，将后面的数据全取

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

IEnumerable<DBItemList> v = list.SkipWhile(p => p.ItemValue >= 2);

foreach (var r in v)

{

Console.WriteLine(r.ItemValue);

}

//print

Reverse

顺序返转

myContext context = new myContext();

IEnumerable<DBItemList> list = context.DBItemList.AsEnumerable();

IEnumerable<DBItemList> v = list.Reverse();

Last,LastOrDefault

集合的最后一个元素,集合中没有会报错,

集合中的最后一个元素,没有则返回类型默认值,对象型默认值为null

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

DBItemList l1 = list.Last();

DBItemList li = list.Last(p=>p.ItemValue==5);

DBItemList lid = list.LastOrDefault(p => p.ItemValue == 15);

if (lid != null)

{

Console.WriteLine(lid.ItemValue);

}

Single,SingleOrDefault

集合中符合条件的唯一元素,集合中没有会报错,集合中有两个以上会报错

集合中符合条件的唯一元素,集合中有两个以上会报错,集合中没有则返回类型默认值,对象型默认值为null

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

DBItemList di = list.Single(p=>p.ItemValue==5);

DBItemList did = list.SingleOrDefault(p => p.ItemValue == 15);

if (did != null)

{

Console.WriteLine(did.ItemValue);

}

Contains

判断集合中是否包含有某一元素

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

DBItemList r = new DBItemList();

r.ItemValue = 3;

bool b = list.Contains(r,new c());

class c : IEqualityComparer<DBItemList>

{

public bool Equals(DBItemList x, DBItemList y)

{

if (x.ItemValue == y.ItemValue)

{

return true;

}

else

{

return false;

}

public int GetHashCode(DBItemList obj)

{

return 0;

}

Distinct

过滤集合中的相同项

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

IEnumerable<DBItemList> v = list.Distinct(new c());

class c : IEqualityComparer<DBItemList>

{

public bool Equals(DBItemList x, DBItemList y)

{

if (x.ItemValue == y.ItemValue)

{

return true;

}

else

{

return false;

}

public int GetHashCode(DBItemList obj)

{

return 0;

}

ElementAt,ElementAtOrDefault

集合中指定索引的元素

集合中指定索引的元素,没有则返回类型默认值,对象型默认值为null

myContext context = new myContext();

List<DBItemList> list = context.DBItemList.ToList();

DBItemList r = list.ElementAt(5);

DBItemList rd = list.ElementAtOrDefault(50);

DefaultIfEmpty

如果集合是的无素为空(count==0),就向集合中插入一个默认元素

DBItemList r=new DBItemList();

r.ItemValue=100;

List<DBItemList> list = new List<DBItemList>();

var pp = list.DefaultIfEmpty(r);

SelectMany

myContext context = new myContext();

List<DBItemList> query = context.DBItemList.ToList();

IEnumerable<string> ls=query.SelectMany(p => p.NameID.Split('0'));

foreach (string r in ls)

{

Console.WriteLine(r);

}

Lambda表达式

List<string> ls = new List<string>() { "wxd/1", "lzm/2", "wxwinter/3" };

var li = ls.SelectMany(p => p.Split('/'));

foreach (var s in li)

{

Console.WriteLine(s);

}

对应Select效果

var ll = ls.Select(p => p.Split('/'));

foreach (var s in ll)

{

foreach (var ss in s)

{

Console.WriteLine(ss);

}

SequenceEqual

比较两个序列是否相等，可以指定相等比较方法

myContext context = new myContext();

List<DBItemList> list1 = context.DBItemList.Where(p => p.ItemID == "a" ).ToList();

List<DBItemList> list2 = context.DBItemList.Where(p => p.ItemID == "a").ToList();

bool b = list1.SequenceEqual(list2);

Console.WriteLine(b);

//print:True

比起 LINQ to SQL，EF 除了提供 LINQ 查询方式, 还提供了 Entity SQL language

ESQL 类似 Hibernate 的 HSQL，ESQL 与SQL 语言的语法相似，以字符串的方式执行

esql的查询结果集 ObjectQuery

ObjectQuery<实体>

myContext context = new myContext();

string esql = "SELECT VALUE DBItemList FROM myContext.DBItemList";

// ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql, context);

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine(r.NameID);

}

myContext context = new myContext();

string esql = "SELECT VALUE it FROM myContext.DBItemList as it";

// ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql, context);

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine(r.NameID);

}

ObjectQuery<DbDataRecord>

myContext context = new myContext();

string esql = "SELECT it.NameID FROM myContext.DBItemList as it";

//ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esql, context);

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine(r["NameID"].ToString());

}

ObjectQuery<简单类型>

myContext context = new myContext();

string esql = "SELECT value count(it.NameID) FROM myContext.DBItemList as it";

// ObjectQuery<int> query = new ObjectQuery<int>(esql, context);

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

myContext context = new myContext();

string esql = "SELECT value it.NameID FROM myContext.DBItemList as it";

// ObjectQuery<int> query = new ObjectQuery<int>(esql, context);

ObjectQuery<string> query = context.CreateQuery<string>(esql);

foreach (string n in query)

{

Console.WriteLine(n);

}

esql的使用

可以在

ObjectQuery的Linq方法,
构造ObjectQuery,
context.CreateQuery返方法,

中使用esql,并得到返回的榄查询结果ObjectQuery

it关键字

[it] 出现在 ESQL 中, 由 ObjectQuery<T>.Name 属性设定，用于标示源查询对象(ObjectQuery)的名称，

类似于 "SELECT * FROM Tab as it WHERE it.ItemValue =14" 。

可以将这个默认值 "it" 改成其他字符串。

myContext context = new myContext();

context.DBItemList.Name = "wxd";

ObjectQuery<DBItemList> list = context.DBItemList.Where("wxd.ItemValue=5");

myContext context = new myContext();

var sql = "SELECT VALUE DBItemList FROM myContext.DBItemList";

var query = new ObjectQuery<DBItemList>(sql, context);

query.Name = "wxd";

ObjectQuery<DBItemList> list = query.Where("wxd.ItemValue=@v", newObjectParameter("v", 5));

value 关键字

value 后只能返回一个成员

myContext context = new myContext();

string esql = "SELECT value AVG(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

/* print:

string esql = "select value it.ItemID from myContext.DBItemList as it";

ObjectQuery<string> query = context.CreateQuery<string>(esql);

foreach (string r in query)

{

Console.WriteLine(r);

}

myContext context = new myContext();

string esql = "select value row( it.ItemValue ,it.NameID,'wxd' as wxwinter) from myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1},{2}", r["ItemValue"], r["NameID"], r["wxwinter"]);

}

查询参数的使用

myContext context = new myContext();

string esql = "SELECT VALUE it FROM myContext.DBItemList as it where it.ItemValue=@v1 or it.NameID=@v2";

ObjectParameter v1 = new ObjectParameter("v1", 3);

ObjectParameter v2 = new ObjectParameter("v2", "n01");

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql,v1,v2);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}",r.NameID,r.ItemValue);

}

中文字段

使用[]将字段括起来

myContext context = new myContext();

ObjectQuery<typeTest> query = context.typeTest.Where("it.值 ==22.22");

System.Console.WriteLine(query.CommandText);

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}", r.a, r.b, r.c, r.d, r.e, r.值);

}

myContext context = new myContext();

ObjectQuery<typeTest> query = context.typeTest.Where("it.[值] ==22.22");

System.Console.WriteLine(query.CommandText);

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}", r.a, r.b, r.c, r.d, r.e, r.值);

}

得到esql与sql字串

myContext context = new myContext();

string esql = "SELECT VALUE it FROM myContext.DBItemList as it";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

Console.WriteLine(query.CommandText);

Console.WriteLine(query.ToTraceString())

SELECT VALUE it FROM myContext.DBItemList as it

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

CommandText属性

得到esql字串

ToTraceString方法

得到sql字串

ObjectQuery的Linq方法

Where

用字符串为条件进行查询

ObjectQuery<T> Where(string predicate, params ObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<DBItemList> list = context.DBItemList.Where("(it.ItemValue=5 or it .ItemValue=5) and it.NameID='n01'");

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE (([Extent1].[ItemValue] = 5) OR ([Extent1].[ItemValue] = 5)) AND([Extent1].[NameID] = 'n01')

OrderBy

排序

ObjectQuery<T> OrderBy(string keys, params ObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.OrderBy("it.ItemValue,it.ItemID desc");

foreach (var r in query)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

ORDER BY [Extent1].[ItemValue] ASC, [Extent1].[ItemID] DESC

Select

射影

ObjectQuery<DbDataRecord> Select(string projection, params ObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<DbDataRecord> list = context.DBItemList.Select(" it.ItemValue as a,it.NameID ");

SELECT

1 AS [C1],

[Extent1].[ItemValue] AS [ItemValue],

[Extent1].[NameID] AS [NameID]

FROM [dbo].[DBItemList] AS [Extent1]

SelectValue(projection)

返回只有一组字段的数组

ObjectQuery<TResultType> SelectValue<TResultType>(string projection, paramsObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<int> query = context.DBItemList.SelectValue<int>("it.ItemValue + it.AutoID");

foreach (var r in query)

{

Console.WriteLine(r);

}

SELECT

[Extent1].[ItemValue] + [Extent1].[AutoId] AS [C1]

FROM [dbo].[DBItemList] AS [Extent1]

Top(count)

集合的前n个元素

count : 前n个元素

ObjectQuery<T> Top(string count, params ObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.Top("3"); ;

foreach (var r in query)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT TOP (3)

[c].[AutoId] AS [AutoId],

[c].[NameID] AS [NameID],

[c].[ItemID] AS [ItemID],

[c].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [c]

Skip(keys,count)

跳过集合的前n个元素,

keys : 用于排序的字段

count : 要跳过的记录个数

ObjectQuery<T> Skip(string keys, string count, params ObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.Skip("it.ItemValue", "5");

foreach (var r in query)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM ( SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS[NameID], [Extent1].[ItemID] AS [ItemID], [Extent1].[ItemValue] AS[ItemValue], row_number() OVER (ORDER BY [Extent1].[ItemValue] ASC) AS[row_number]

FROM [dbo].[DBItemList] AS [Extent1]

) AS [Extent1]

WHERE [Extent1].[row_number] > 5

ORDER BY [Extent1].[ItemValue] ASC

分页 Skip Top

Skip与Top一起使用

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.Skip("it.ItemValue", "5").Top("3"); ;

foreach (var r in query)

{

Console.WriteLine("{0},{1},{2},{3}", r.AutoId, r.ItemID, r.NameID, r.ItemValue);

}

SELECT TOP (3)

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM ( SELECT [Extent1].[AutoId] AS [AutoId], [Extent1].[NameID] AS[NameID], [Extent1].[ItemID] AS [ItemID], [Extent1].[ItemValue] AS[ItemValue], row_number() OVER (ORDER BY [Extent1].[ItemValue] ASC) AS[row_number]

FROM [dbo].[DBItemList] AS [Extent1]

) AS [Extent1]

WHERE [Extent1].[row_number] > 5

ORDER BY [Extent1].[ItemValue] ASC

GroupBy(keys,projection)

分组

keys: GROUP BY的字段

projection : Select 的内容

ObjectQuery<DbDataRecord> GroupBy(string keys, string projection, paramsObjectParameter[] parameters);

myContext context = new myContext();

ObjectQuery<DbDataRecord> query = context.DBItemList.GroupBy("it.ItemID","it.ItemID,Sum(it.ItemValue) as ValueSum");

foreach (var r in query)

{

Console.WriteLine("{0},{1}", r["ItemID"], r["ValueSum"]);

}

a,23

b,8

c,23

SELECT

1 AS [C1],

[GroupBy1].[K1] AS [ItemID],

[GroupBy1].[A1] AS [C2]

FROM ( SELECT

[Extent1].[ItemID] AS [K1],

SUM([Extent1].[ItemValue]) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1]

GROUP BY [Extent1].[ItemID]

) AS [GroupBy1]

SELECT it.ItemID,Sum(it.ItemValue) as ValueSum

FROM ( [DBItemList] ) AS it

GROUP BY it.ItemID

Include(path)

加载关联数据,参数为实体的[导航属性]的字串,调用Include("导航属性")后,关联数据会加载,这样就不用在[实体.导航属性]上调用Load()方法

ObjectQuery<T> Include(string path);

myContext context = new myContext();

var r = context.DBItem.Include("DBItemList");

foreach (var dbitem in r)

{

foreach (var dbitemlist in dbitem.DBItemList)

{

Console.WriteLine("{0},{1}", dbitemlist.NameID, dbitemlist.ItemValue);

}

效果与下例相同

myContext context = new myContext();

var r = context.DBItem;

foreach (var dbitem in r)

{

dbitem.DBItemList.Load();

foreach (var dbitemlist in dbitem.DBItemList)

{

Console.WriteLine("{0},{1}", dbitemlist.NameID, dbitemlist.ItemValue);

}

esql注释,成员访问,分行

注释	--
成员访问	.
分行	;

esql运算符

算术运算符

加	+
减	-
乘	*
除	/
模	%
负	-

比效运算符

等于	=
大于	>
大于等于	>=
空判断	IS NOT NULL IS NULL
小于	<
小天等于	<=
不等于	!= <>
字符比效	LIKE '' NOT LIKE ''
字符比效	% : _ : [ ] : [^] :

逻辑运算符

与

AND

非

NOT

或

区间

BETWEEN

之间

BETWEEN n AND m

NOT BETWEEN n AND m

myContext context = new myContext();

string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue BETWEEN 2 and 4";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.Where(" it.ItemValue not BETWEEN 2 and 4");

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

在集合中

IN {v,v}

NOT IN{v,v}

myContext context = new myContext();

string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue IN {1,2,3}";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.Where("it.ItemValue not IN {1,2,3}");

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

EXISTS

存在

EXISTS(select from)

NOT EXISTS(select from)

myContext context = new myContext();

string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE exists(Select VALUE it2 From DBItem as it2 Where it2.ItemID=it.ItemID )";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

myContext context = new myContext();

ObjectQuery<DBItemList> query = context.DBItemList.Where("exists(Select VALUE it2 From DBItem as it2 Where it2.ItemID=it.ItemID )");

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

分页

SELECT VALUE it FROM ( [DBItemList] ) AS it

ORDER BY it.ItemValue

SKIP 5

LIMIT 3

集合运算

Union

(合集)

连接不同集合

UNION --自动过滤相同项

UNION ALL --两个集合的相同项都会返回

myContext context = new myContext();

string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ) UNION (select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' )";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

EXCEPT

(左并集)

从集合中删除其与另一个集合中相同的项

myContext context = new myContext();

string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ) EXCEPT (select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' )";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

INTERSECT

（交集）

获取不同集合的相同项

myContext context = new myContext();

string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'a' ) INTERSECT (select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID == 'b' )";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

ANYELEMENT

集合中的第一个

myContext context = new myContext();

string esql = "ANYELEMENT(select value it from myContext.DBItemList as it where it.ItemID == 'a') ";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

//如果集合中有两个以上,只返回第一个到集合中

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

SELECT

[Element1].[AutoId] AS [AutoId],

[Element1].[NameID] AS [NameID],

[Element1].[ItemID] AS [ItemID],

[Element1].[ItemValue] AS [ItemValue]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

LEFT OUTER JOIN (SELECT TOP (1)

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE [Extent1].[ItemID] = 'a' ) AS [Element1] ON 1 =1

OVERLAPS

两个集合是否有相交部份

myContext context = new myContext();

string esql = "(select value it from myContext.DBItemList as it where it.ItemID == 'c' || it.ItemID=='b' ) OVERLAPS (select value it from myContext.DBItemList as it where it.ItemID == 'a' || it.ItemID=='b')";

ObjectQuery<bool> query = context.CreateQuery<bool>(esql);

foreach (bool r in query)

{

Console.WriteLine(r);

}

//print: True

SELECT

CASE WHEN ( EXISTS (SELECT

cast(1 as bit) AS [C1]

FROM (SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE ([Extent1].[ItemID] = 'c') OR([Extent1].[ItemID] = 'b')

INTERSECT

SELECT

[Extent2].[AutoId] AS [AutoId],

[Extent2].[NameID] AS [NameID],

[Extent2].[ItemID] AS [ItemID],

[Extent2].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent2]

WHERE ([Extent2].[ItemID] = 'a') OR([Extent2].[ItemID] = 'b')) AS [Intersect1]

)) THEN cast(1 as bit) WHEN ( NOT EXISTS (SELECT

cast(1 as bit) AS [C1]

FROM (SELECT

[Extent3].[AutoId] AS [AutoId],

[Extent3].[NameID] AS [NameID],

[Extent3].[ItemID] AS [ItemID],

[Extent3].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent3]

WHERE ([Extent3].[ItemID] = 'c') OR([Extent3].[ItemID] = 'b')

INTERSECT

SELECT

[Extent4].[AutoId] AS [AutoId],

[Extent4].[NameID] AS [NameID],

[Extent4].[ItemID] AS [ItemID],

[Extent4].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent4]

WHERE ([Extent4].[ItemID] = 'a') OR([Extent4].[ItemID] = 'b')) AS [Intersect2]

)) THEN cast(0 as bit) END AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

Set

去掉重复项

myContext context = new myContext();

string esql = "set(select value it.ItemID from myContext.DBItemList as it)";

ObjectQuery<string> query = context.CreateQuery<string>(esql);

foreach (string r in query)

{

Console.WriteLine(r);

}

//去掉了重复项

SELECT

[Distinct1].[ItemID] AS [ItemID]

FROM ( SELECT DISTINCT

[Extent1].[ItemID] AS [ItemID]

FROM [dbo].[DBItemList] AS [Extent1]

) AS [Distinct1]

esql函数

统计类

Avg

平均值

myContext context = new myContext();

string esql = "SELECT value AVG(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

/* print:

BigCount

个数(long)

myContext context = new myContext();

string esql = "SELECT value BigCount(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<long> query = context.CreateQuery<long>(esql);

foreach (long n in query)

{

Console.WriteLine(n);

}

/* print:

Count

个数(int)

myContext context = new myContext();

string esql = "SELECT value Count(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

/* print:

Max

最大值

myContext context = new myContext();

string esql = "SELECT value Max(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

/* print:

Min

最小值

myContext context = new myContext();

string esql = "SELECT value Min(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

/* print:

Sum

合计

myContext context = new myContext();

string esql = "SELECT value Sum(it.ItemValue) FROM myContext.DBItemList as it";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int n in query)

{

Console.WriteLine(n);

}

/* print:

联合使用

myContext context = new myContext();

string esql = "SELECT Max(it.ItemValue) as Max , Min(it.ItemValue) as Min FROM myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("Max:{0},Min:{1}", r["Max"], r["Min"]);

}

/* print:

Max:6,Min:1

与group by一起使用

myContext context = new myContext();

string esql = "SELECT ID as ItemID , Max(it.ItemValue) as Max , Min(it.ItemValue) as Min FROM myContext.DBItemList as it group by it.ItemID as ID";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("ItemID:{0}, Max:{1},Min:{2}", r["ItemID"], r["Max"], r["Min"]);

}

/* print:

ItemID:a, Max:6,Min:2

ItemID:b, Max:5,Min:1

ItemID:c, Max:6,Min:2

数学类

Abs

绝对值

Abs(-2)

Round

随机数

Round(748.58)

日期

CurrentDateTime()
CurrentDateTimeOffset()
CurrentUtcDateTime()
Day( expression )	Day(cast('03/12/1998' as DateTime)) --返回:12
GetTotalOffsetMinutes	--返回: SQL Server 2008 only
Hour ( expression )	Hour(cast('22:35:5' as DateTime)) --返回:22
Minute( expression )	Minute(cast('22:35:5' as DateTime)) --返回:35
Month (expression)	Month(cast('03/12/1998' as DateTime)) --返回:3
Second( expression )	Second(cast('22:35:5' as DateTime)) --返回:5
Year( expression )	Year(cast('03/12/1998' as DateTime)) --返回:1998

字符

Concat ( string1, string2) 字符串连接	Concat('abc', 'xyz') --返回:abcxyz
IndexOf( string1, string2) 字符串位置查找	IndexOf('xyz', 'abcxyz') --返回:4
Length ( string ) 字符串长度	Legth('abcxyz') --返回:6
Reverse ( string ) 字符串反转	Reverse('abcd') --返回:dcba
ToLower( string ) 大写转小写	ToLower('ABC') --返回:abc
ToUpper( string ) 小写转大写	ToUpper('abc') --返回:ABC
Trim( string ) 去两端空格	Trim(' abc ') --返回:abc
LTrim( string ) 去左端空格	LTrim(' abc') --返回:abc
RTrim( string ) 去右端空格
Left ( string, length) 左端截取	Left('abcxyz', 3) --返回:abc
Right ( string, length) 右端截取	Right('abcxyz', 3) --返回:xyz
Substring ( string, start, length) 两端截取	Substring('abcxyz', 4, 3) --返回:xyz

esql语句

查询语句

SELECT

myContext context = new myContext();

string esql = "SELECT it.ItemValue as a,it.NameID FROM [DBItemList] AS it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1}", r["a"], r["NameID"]);

}

SELECT

1 AS [C1],

[Extent1].[ItemValue] AS [ItemValue],

[Extent1].[NameID] AS [NameID]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE

myContext context = new myContext();

string esql = "SELECT VALUE it FROM [DBItemList] AS it WHERE (it.ItemValue=5 or it .ItemValue=5) and it.NameID='n01' ";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

WHERE (([Extent1].[ItemValue] = 5) OR ([Extent1].[ItemValue]= 5)) AND ([Extent1].[NameID] = 'n01')

GROUP BY

myContext context = new myContext();

string esql = "SELECT it.ItemID,Sum(it.ItemValue) as ValueSum FROM [DBItemList] AS it GROUP BY it.ItemID ";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1}", r["ItemID"], r["ValueSum"]);

}

SELECT

1 AS [C1],

[GroupBy1].[K1] AS [ItemID],

[GroupBy1].[A1] AS [C2]

FROM ( SELECT

[Extent1].[ItemID] AS [K1],

SUM([Extent1].[ItemValue]) AS [A1]

FROM [dbo].[DBItemList] AS [Extent1]

GROUP BY [Extent1].[ItemID]

) AS [GroupBy1]

ORDER BY

myContext context = new myContext();

string esql = "SELECT VALUE it FROM [DBItemList] AS it ORDER BY it.ItemValue,it.ItemID desc ";

ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql);

foreach (DBItemList r in query)

{

Console.WriteLine("{0},{1}", r.ItemID, r.ItemValue);

}

SELECT

[Extent1].[AutoId] AS [AutoId],

[Extent1].[NameID] AS [NameID],

[Extent1].[ItemID] AS [ItemID],

[Extent1].[ItemValue] AS [ItemValue]

FROM [dbo].[DBItemList] AS [Extent1]

ORDER BY [Extent1].[ItemValue] ASC, [Extent1].[ItemID] DESC

HAVING

myContext context = new myContext();

string esql = "SELECT it.ItemID,Count(it.ItemValue) as ValueSum FROM DBItemList AS it GROUP BY it.ItemID HAVING SUM(it.ItemValue) > 5";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1}", r["ItemID"], r["ValueSum"]);

}

SELECT

1 AS [C1],

[GroupBy1].[K1] AS [ItemID],

[GroupBy1].[A2] AS [C2]

FROM ( SELECT

[Extent1].[ItemID] AS [K1],

SUM([Extent1].[ItemValue]) AS [A1],

COUNT([Extent1].[ItemValue]) AS [A2]

FROM [dbo].[DBItemList] AS [Extent1]

GROUP BY [Extent1].[ItemID]

) AS [GroupBy1]

WHERE [GroupBy1].[A1] > 5

JOIN

Cross Joins

Inner Joins

Left Outer Joins

Right Outer Joins

Full Outer Joins

CASE语句

CASE WHEN THEN ELSE END

myContext context = new myContext();

string esql = "select it.ItemID, it.ItemValue ,(Case when it.ItemValue =1 then '差' when it.ItemValue between 2 and 4 then '好' else '其他' end) as ItemValueRemarks from myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1},{2}", r["ItemID"], r["ItemValue"], r["ItemValueRemarks"]);

}

c,4,好

c,5,其他

c,2,好

c,3,好

b,5,其他

c,6,其他

b,2,好

b,1,差

c,3,好

a,4,好

a,5,其他

a,2,好

a,3,好

a,6,其他

a,3,好

esql 类型

简单类型

Null

is Null

is not Null

myContext context = new myContext();

ObjectQuery<typeTest> query = context.typeTest.Where("it.b is not Null");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

Boolean

True,False

myContext context = new myContext();

ObjectQuery<typeTest> query = context.typeTest.Where("it.e==True");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

Integer

Float,Double

Decimal

123

123.456

23.34

myContext context = new myContext();

ObjectQuery<typeTest> query = context.typeTest.Where("it.c==123");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

String

"abcd"

N"U字符"

'abcd'

myContext context = new myContext();

// ObjectQuery<typeTest> query = context.typeTest.Where("it.b==N'冬冬'");

ObjectQuery<typeTest> query = context.typeTest.Where("it.b==\"冬冬\" ");

// ObjectQuery<typeTest> query = context.typeTest.Where("it.b=='冬冬'");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

DateTime

DATETIME'2007-11-11 22:22'

DATETIME'2007-11-11 01:01:00.0000000'

myContext context = new myContext();

// ObjectQuery<typeTest> query = context.typeTest.Where("it.d==DATETIME'1977-11-11 00:00:00.000'");

ObjectQuery<typeTest> query = context.typeTest.Where("it.d==cast('1977-11-11' as System.DateTime)");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

Time

TIME'22:11'

TIME'01:02:03.1234567'

DateTimeOffset

DATETIMEOFFSET'2007-11-11 22:11 +02:00'

DATETIMEOFFSET'2007-11-11 01:01:00.0000000 -02:00'

Binary

Binary'00ffaabb'

X'ABCabc'

BINARY '0f0f0f0F0F0F0F0F0F0F'

X'' –空

Guid

Guid'0321AF86-0AA5-4a86-A086-1D789FA54AA3'

GUID '0321AF86-0AA5-4a86-A086-1D789FA54AA3'

myContext context = new myContext();

ObjectQuery<typeTest> query = context.typeTest.Where("it.a==Guid'0321af86-0aa5-4a86-a086-1d789fa54aa3'");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

REF

myContext context = new myContext();

//string esql = "SELECT it.ItemID FROM DBItem as it";

string esql = "SELECT REF(it).ItemID FROM DBItem as it";

ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in v)

{

Console.WriteLine("{0}", r[0]);

}

ROW

myContext context = new myContext();

string esql = "select value row( it.ItemValue ,it.NameID,'wxd' as wxwinter) from myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1},{2}", r["ItemValue"], r["NameID"], r["wxwinter"]);

}

myContext context = new myContext();

string esql = "select row( it.ItemValue ,it.NameID) as wxd ,it.ItemID from myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

DbDataRecord v = r["wxd"] as DbDataRecord;

Console.WriteLine("{0},{1},{2}", r["ItemID"],v["ItemValue"],v["NameID"]);

}

集合

MULTISET(1,2,3,4)

{1,2,3,4}

SELECT VALUE it FROM [DBItemList] AS it WHERE it.ItemValue IN {1,2,3}

myContext context = new myContext();

string esql = "{1,2,3} ";

ObjectQuery<int> query = context.CreateQuery<int>(esql);

foreach (int r in query)

{

System.Console.WriteLine(r);

}

SELECT

[UnionAll2].[C1] AS [C1]

FROM (SELECT

[UnionAll1].[C1] AS [C1]

FROM (SELECT

1 AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

UNION ALL

SELECT

2 AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable2]) AS[UnionAll1]

UNION ALL

SELECT

3 AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable3]) AS[UnionAll2]

myContext context = new myContext();

string esql = "{row(1 as a,'wxd' as wxwinter),row(2 as a,'lzm' as wxwinter),row(3 as a,'wxwinter' as wxwinter)} ";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

System.Console.WriteLine("{0},{1}",r["a"],r["wxwinter"]);

}

1,wxd

2,lzm

3,wxwinter

SELECT

1 AS [C1],

CASE WHEN ([UnionAll2].[C1] = 0) THEN 1 WHEN ([UnionAll2].[C1] = 1)THEN 2 ELSE 3 END AS [C2],

CASE WHEN ([UnionAll2].[C1] = 0) THEN 'wxd' WHEN ([UnionAll2].[C1] = 1)THEN 'lzm' ELSE 'wxwinter' END AS [C3]

FROM (SELECT

[UnionAll1].[C1] AS [C1]

FROM (SELECT

0 AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable1]

UNION ALL

SELECT

1 AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable2]) AS[UnionAll1]

UNION ALL

SELECT

2 AS [C1]

FROM ( SELECT cast(1 as bit) AS X ) AS [SingleRowTable3]) AS[UnionAll2]

Object 返回对像

Select 选出的值可以直接创建为对像后,将对像放入字段中返回

myContext context = new myContext();

string esql = "SELECT [WindowsFormsApplication8].[DBItemEx](it.ItemID + 'b') as myObject FROM DBItem as it";

ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in v)

{

DBItemEx obj = r["myObject"] as DBItemEx;

Console.WriteLine("{0}", obj.ItemID);

}

CAST 类型转换

myContext context = new myContext();

string esql = "select value CAST(it.ItemValue as System.String) from myContext.DBItemList as it";

ObjectQuery<string> query = context.CreateQuery<string>(esql);

foreach (string r in query)

{

Console.WriteLine(r);

}

myContext context = new myContext();

string esql = "using System;select value CAST(it.ItemValue as String) from myContext.DBItemList as it";

ObjectQuery<string> query = context.CreateQuery<string>(esql);

foreach (string r in query)

{

Console.WriteLine(r);

}

CAST( d as Edm.Decimal(16, 2) )

OFTYPE

OFTYPE ( expression, [ONLY] test_type )

myContext context = new myContext();

string esql = "OFTYPE(((SELECT VALUE it FROM DBItem as it) ),[WindowsFormsApplication8].[DBItemEx])";

ObjectQuery<DBItemEx> v = context.CreateQuery<DBItemEx>(esql);

与如下效果相同

myContext context = new myContext();

ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

TREAT

myContext context = new myContext();

string esql = "SELECT TREAT(it AS [WindowsFormsApplication8].[DBItemEx]) FROM DBItem AS it";

ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in v)

{

DBItemEx obj = r[0] as DBItemEx;

if (obj != null)

{

Console.WriteLine("{0}", obj.ItemID);

}

与如下效果类似

myContext context = new myContext();

ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

IS 类型判断

myContext context = new myContext();

string esql = "SELECT TREAT(it AS [WindowsFormsApplication8].[DBItemEx]) FROM DBItem AS it WHERE it IS OF ([WindowsFormsApplication8].[DBItemEx])";

ObjectQuery<DbDataRecord> v = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in v)

{

DBItemEx obj = r[0] as DBItemEx;

// if (obj != null)

{

Console.WriteLine("{0}", obj.ItemID);

}

与如下效果类似

myContext context = new myContext();

ObjectQuery<DBItemEx> v = context.DBItem.OfType<DBItemEx>();

esql Namespace

使用SqlServer函数

using SqlServer;

myContext context = new myContext();

string esql = "using SqlServer;select it.ItemValue ,LEN(it.NameID) as NameIDLEN from myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1}",r["ItemValue"],r["NameIDLEN"]);

}

SqlServer.函数

myContext context = new myContext();

string esql = "select it.ItemValue ,SqlServer.LEN(it.NameID) as NameIDLEN from myContext.DBItemList as it";

ObjectQuery<DbDataRecord> query = context.CreateQuery<DbDataRecord>(esql);

foreach (DbDataRecord r in query)

{

Console.WriteLine("{0},{1}",r["ItemValue"],r["NameIDLEN"]);

}

SELECT

1 AS [C1],

[Extent1].[ItemValue] AS [ItemValue],

LEN([Extent1].[NameID]) AS [C2]

FROM [dbo].[DBItemList] AS [Extent1]

使用NET的数据类型

myContext context = new myContext();

string esql = "using System;select value CAST(it.ItemValue as String) from myContext.DBItemList as it";

ObjectQuery<string> query = context.CreateQuery<string>(esql);

foreach (string r in query)

{

Console.WriteLine(r);

}

myContext context = new myContext();

// ObjectQuery<typeTest> query = context.typeTest.Where("it.d==DATETIME'1977-11-11 00:00:00.000'");

ObjectQuery<typeTest> query = context.typeTest.Where("it.d==cast('1977-11-11' as System.DateTime)");

foreach (typeTest r in query)

{

Console.WriteLine("{0},{1},{2},{3},{4},{5}",r.a,r.b,r.c,r.d,r.e,r.值);

}

esql关系,导航

KEY

myContext context = new myContext();

string esql="SELECT VALUE [TargetEntity] FROM (SELECT VALUE x FROM [myContext].[FK_DBItemList_DBItem] AS x WHERE Key(x.[DBItem]) = ROW(@EntityKeyValue1 AS EntityKeyValue1)) AS [AssociationEntry] INNER JOIN [myContext].[DBItemList] AS [TargetEntity] ON Key([AssociationEntry].[DBItemList]) = Key(Ref([TargetEntity]))";

ObjectQuery<DBItemList> dbitemlist = context.CreateQuery<DBItemList>(esql, newObjectParameter("EntityKeyValue1", "a"));

foreach (DBItemList r in dbitemlist)

{

Console.WriteLine("{0},{1},{2}", r.AutoId, r.ItemValue, r.NameID);

}

效果同下

myContext context = new myContext();

ObjectQuery<DBItemList> dbitemlist = context.DBItem.First(p => p.ItemID =="a").DBItemList.CreateSourceQuery();

foreach (DBItemList r in dbitemlist)

{

Console.WriteLine("{0},{1},{2}", r.AutoId, r.ItemValue, r.NameID);

}

Entity Framework 基本概念

概念

ADO.NET Entity Framework

架构

说明

EntityConnection

EntityCommand

通过EntityDataReader 方式的数据访问

通过ObjectContext返回ObjectQuery<T> 方式的数据访问

模型结构

模型关系说明

模型设计器结构说明

EDM

Model设计器

edmx文件

Context

实体类

使用

使用向导创建模型

映射基本规则

映射条件

继承

多表联合

关联

[(1)—(*)] 关联

表

设置

操作数据

[(1)—(1)]关联

表

设置

操作数据

[(1)—(0..1)]关联

[(*)—(*)]关联

表

显示中转方式

隐示中转方式

操作数据

映射存储过程与函数

返回表型存储过程

存储过程

使用向导生成映射

代码实现

命令型存储过程

存储过程

使用向导生成映射

代码实现

参数返回值型存储过程

存储过程

使用向导生成映射

代码实现

说明

Context操作数据

AddObject 添加实体

DeleteObject 删除实体

Detach 分离实体

修改实体

ApplyPropertyChanges 修改实体

Attach / AttachTo 附加实体

CreateEntityKey 创建EntityKey

EntityKey

GetObjectByKey/TryGetObjectByKey 通过EntityKey得到实体

CreateQuery 创建查询

状态管理

EntityState 状态枚举

Context.ObjectStateManager 管理记录的状态

GetObjectStateEntry 根据实体对象或实体主键得到状态实体

TryGetObjectStateEntry 根据实体对象或实体主键得到状态实体

GetObjectStateEntries 根据状态类型得到状态实体集合

ObjectStateManagerChanged 事件

ObjectStateEntry 对象

基本属性

State 状态属性

CurrentValues 当前值

OriginalValues 原始值

GetModifiedProperties 得到被修改的属性

SetModified,SetModifiedProperty 标记为修改

Delete 标记为删除

AcceptChanges 方法

保存修改到数据库

[()—()]关联