精进不休 .NET 4.0 (8) - ADO.NET Entity Framework 4.0 Self Tracking Entity

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精进不休 .NET 4.0 (8) - ADO.NET Entity Framework 4.0 Self Tracking Entity

作者： webabcd


介绍
ADO.NET Entity Framework 4.0 的新增功能

• 对 Self Tracking Entity（实体状态自跟踪）的支持，基于 POCO 
• WCF 结合 Self Tracking Entity 的应用 

示例
1、Self Tracking Entity 的 Demo
SelfTrackingDemo/BLL.cs

/*
* ADO.NET Entity Framework 4.0 - 对 Self Tracking Entity（实体状态自跟踪）的支持，基于 POCO
*         1、不通过 WCF 使用 Self Tracking Entity 需要手动调用 StartTracking()
*         2、MarkAsAdded(), MarkAsModified(), MarkAsDeleted() 会自动 StartTracking()
*         3、ApplyChanges() 的作用是：绑定实体到上下文，通过 ChangeObjectState 改变实体的状态，通过 ChangeRelationshipState 改变关联实体的状态
*    
* 本 Demo 演示如何通过 Self Tracking Entity 来实现对单表的增删改查
*         如果涉及到关联实体，可以参考 http://webabcd.blog.51cto.com/1787395/341378 中的“对外键的支持”的 Demo
*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace SelfTrackingDemo
{
         public class BLL
        {
                // 取全部产品类别的实体集合
List GetCategories() List GetCategories()
                {
                        using (SelfTrackingEntities ctx = new SelfTrackingEntities())
                        {
                                var result = ctx.ProductCategories.ToList();
                                return result;
                        }
                }

                // 根据 id 取产品类别实体
ProductCategory GetCategory() ProductCategory GetCategory(int categoryId)
                {
                        using (SelfTrackingEntities ctx = new SelfTrackingEntities())
                        {
                                var result = ctx.ProductCategories.Single(c => c.ProductCategoryID == categoryId);
                                return result;
                        }
                }

                // 根据产品类别实体更新数据库中的相关数据
void UpdateCategory() void UpdateCategory(ProductCategory category)
                {
                        using (SelfTrackingEntities ctx = new SelfTrackingEntities())
                        {
                                // ApplyChanges() 的内部逻辑为：绑定实体到上下文，通过 ChangeObjectState 改变实体的状态，通过 ChangeRelationshipState 改变关联实体的状态
                                ctx.ProductCategories.ApplyChanges(category);

                                // 根据实体的状态，实现对实体的 添加、更新、删除 操作
                                var affectedRow = ctx.SaveChanges();
                        }
                }

                // 根据产品类别实体删除数据库中的相关数据
void DeleteCategory() void DeleteCategory(ProductCategory category)
                {
                        // 标记该实体为删除状态
                        category.MarkAsDeleted();

                        UpdateCategory(category);
                }

                // 根据产品类别实体向数据库添加新的数据
void AddCategory() void AddCategory(ProductCategory category)
                {
                        UpdateCategory(category);    
                }
        }
}

 

SelfTrackingDemo/Demo.aspx

<%@ Page Language= "C#" AutoEventWireup= "true" CodeBehind= "Demo.aspx.cs" Inherits= "SelfTrackingDemo.Demo" %>

PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
"http://www.w3.org/1999/xhtml">
"server">
        


        

"form1" runat= "server">
        

                "ListView1" runat= "server" DataSourceID= "ObjectDataSource1" DataKeyNames= "ProductCategoryID"
                        InsertItemPosition= "LastItem" OnItemUpdating= "ListView1_ItemUpdating">
                        
                                
                                        
                                                "UpdateButton" runat= "server" CommandName= "Update" Text= "Update" />
                                                "CancelButton" runat= "server" CommandName= "Cancel" Text= "Cancel" />
                                        
                                        
                                                 
                                        
                                        
                                                 
                                        
                                        
                                                "NameTextBox" runat= "server" Text= '<%# Bind("Name") %>' />
                                        
                                        
                                                 
                                        
                                        
                                                 
                                        
                                
                        
                        
                                
                                        
                                                "InsertButton" runat= "server" CommandName= "Insert" Text= "Insert" />
                                                "CancelButton" runat= "server" CommandName= "Cancel" Text= "Clear" />
                                        
                                        
                                                 
                                        
                                        
                                                 
                                        
                                        
                                                "NameTextBox" runat= "server" Text= '<%# Bind("Name") %>' />
                                        
                                        
                                                 
                                        
                                        
                                                 
                                        
                                
                        
                        
                                
                                        
                                                "DeleteButton" runat= "server" CommandName= "Delete" Text= "Delete" />
                                                "EditButton" runat= "server" CommandName= "Edit" Text= "Edit" />
                                        
                                        
                                                "ProductCategoryIDLabel" runat= "server" Text= '<%# Eval("ProductCategoryID") %>' />
                                        
                                        
                                                "ParentProductCategoryIDLabel" runat= "server" Text= '<%# Eval("ParentProductCategoryID") %>' />
                                        
                                        
                                                "NameLabel" runat= "server" Text= '<%# Eval("Name") %>' />
                                        
                                        
                                                "rowguidLabel" runat= "server" Text= '<%# Eval("rowguid") %>' />
                                        
                                        
                                                "ModifiedDateLabel" runat= "server" Text= '<%# Eval("ModifiedDate") %>' />
                                        
                                
                        
                        
                                "itemPlaceholderContainer" runat= "server" border= "0" style="">
                                        "server" style="">
                                                
                                                
                                                
                                                
                                                
                                                
                                        
                                        "itemPlaceholder" runat= "server">
                                        
                                

"server">	"server">                                                         ProductCategoryID	"server">                                                         ParentProductCategoryID	"server">                                                         Name	"server">                                                         rowguid	"server">                                                         ModifiedDate

                        
                
                "ObjectDataSource1" runat= "server" DataObjectTypeName= "SelfTrackingDemo.ProductCategory"
                        DeleteMethod= "DeleteCategory" InsertMethod= "AddCategory" SelectMethod= "GetCategories"
                        TypeName= "SelfTrackingDemo.BLL" OnInserting= "ObjectDataSource1_Inserting" OnDeleting= "ObjectDataSource1_Deleting">
                
        

        

 

SelfTrackingDemo/Demo.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace SelfTrackingDemo
{
         public partial class Demo : System.Web.UI.Page
        {
void Page_Load() void Page_Load(object sender, EventArgs e)
                {
                        
                }

void ObjectDataSource1_Inserting() void ObjectDataSource1_Inserting(object sender, ObjectDataSourceMethodEventArgs e)
                {
                        var category = e.InputParameters[0] as ProductCategory;
                        category.rowguid = Guid.NewGuid();
                        category.ModifiedDate = DateTime.Now;
                }

void ObjectDataSource1_Deleting() void ObjectDataSource1_Deleting(object sender, ObjectDataSourceMethodEventArgs e)
                {
                        
                }

void ListView1_ItemUpdating() void ListView1_ItemUpdating(object sender, ListViewUpdateEventArgs e)
                {
                        BLL bll = new BLL();
                        var category = bll.GetCategory((int)ListView1.DataKeys[e.ItemIndex].Value);

                        // 注意：这里一定要手动调用 StartTracking() 方法，用于跟踪实体状态的改变
                        category.StartTracking();

                        category.Name = e.NewValues[ "Name"].ToString();
                        bll.UpdateCategory(category);

                        ListView1.EditIndex = -1;
                        e.Cancel = true;
                }
        }
}

 

 

未完待续>>

 

 

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