Mvc4开发框架 -（2）Dapper 扩展 ORM 支持
开发框架搭建之初，需要有个良好的ORM。如：Entity Framework，iBatis.NET（myBatis）、PetaPoco。因为个人爱好原因，选择了轻量级的 Dapper 框架。
Dapper google code: http://code.google.com/p/dapper-dot-net/
Dapper github code: https://github.com/SamSaffron/dapper-dot-net
现在对 Dapper 要做的扩展是，支持 Entity 的 CRUD ，如：
entity.RoleId = Guid.New();
... ...
int result = entity.Insert();
result = entity.Update();
result = entity.Delete();
entity = entity.GetEntity();
扩展预期做到以下几点：
（1） 当实体属性赋值有变化时，自动记录（比如：重新赋值主键RoleID）变更属性。
（2） 根据赋值变化记录，可以动态生成查询条件、更新字段语句。这个想法借鉴自EntityFramework。
（3） 能识别实体主键、自动生成列。在新增数据时，不插入到数据库。
接下来，开始设计与开发扩展。
设计图，什么的以后再补了，先贴代码了。
实体模型接口，空方法接口。
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace BpmExpress.Common.Models
{
public interface IDbEntity
{
} }
实体模型抽象类型，基类：
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.Serialization;
using System.Text;
namespace BpmExpress.Common.Models
{
/// <summary>
/// 数据实体基类.
/// </summary>
[Serializable]
public abstract partial class DbEntity : IDbEntity, INotifyPropertyChanged
{
[NonSerialized]
private IList< string> _changedProperties = null;
public event PropertyChangedEventHandler PropertyChanged;
public DbEntity()
{ }
/// <summary>
/// 修改的属性列表.
/// </summary>
internal IList< string> ChangedProperties
{
get
{
if (_changedProperties == null)
_changedProperties = new List< string>();
return _changedProperties;
}
}
protected virtual void OnPropertyChanged( string propertyName)
{
if (! this.ChangedProperties.Contains(propertyName))
{
this.ChangedProperties.Add(propertyName);
}
if ( this.PropertyChanged != null)
{
this.PropertyChanged.Invoke( this, new PropertyChangedEventArgs(propertyName));
}
}
}}
这个抽象类中，最主要的是 ChangedProperties，用存放实体模型变更属性。这样才能实现上面预期的 根据赋值变化记录，可以动态生成查询条件、更新字段语句。
对于 Dapper 扩展如下：
1. 增加
{
if (entity == null)
return 0;
db = GetDataBase(db);
EntityDefinition definition = EntityDefinition.GetEntityDefinition(entity.GetType()); // 获取实体定义
StringBuilder parameters = new StringBuilder();
StringBuilder values = new StringBuilder();
IList<string> changed = null;
if (entity != null && entity.ChangedProperties.Count > 0)
changed = entity.ChangedProperties; // 变更属性
foreach (var propertyName in changed)
{
if (definition.AutoGenerations.Contains(propertyName))
continue;
parameters.AppendFormat("{0},", propertyName);
values.AppendFormat("@{0},", propertyName);
}
if (parameters.Length > 1)
{
parameters.Length = parameters.Length - 1;
values.Length = values.Length - 1;
}
string sql = string.Format("insert into {0}({1}) values ({2})", definition.TableName, parameters, values);
int rowAffected = db.ExecuteNonQuery(sql, entity); // Dapper方法
return rowAffected;
}
2. 删除
{
if (entity == null)
return 0;
db = GetDataBase(db);
EntityDefinition definition = EntityDefinition.GetEntityDefinition(entity.GetType());
IList< string> changed = null;
if (entity != null && entity.ChangedProperties.Count > 0)
changed = entity.ChangedProperties; // 变更属性，生成删除条件
StringBuilder where = new StringBuilder();
if (changed.Count > 0)
{
foreach ( var propertyName in changed)
{
where.AppendFormat( " {0}=@{0} and ", propertyName);
}
where.Length = where.Length - 4;
}
else
{
where.Append(definition.GetPrimaryCommand()); // 获取主键，删除
}
string sql = string.Format( " delete from {0} where {1} ", definition.TableName, where);
Trace(sql);
int rowAffected = db.ExecuteNonQuery(sql, entity); // Dapper
return rowAffected; }
3. 修改
{
if (entity == null)
return 0;
db = GetDataBase(db);
EntityDefinition definition = EntityDefinition.GetEntityDefinition(entity.GetType());
StringBuilder parameters = new StringBuilder();
IList< string> changed = null;
if (entity != null && entity.ChangedProperties.Count > 0)
changed = entity.ChangedProperties; // 变更的字段
if (changed == null || changed.Count == 0)
throw new Data.DbException( " 不存在需要更新的属性 ");
foreach ( var propertyName in changed)
{
if (definition.AutoGenerations.Contains(propertyName))
continue;
parameters.AppendFormat( " {0}=@{0}, ", propertyName);
}
parameters.Length = parameters.Length - 1;
// 根据主键更新
string sql = string.Format( " update {0} set {1} where {2} ", definition.TableName, parameters, definition.GetPrimaryCommand());
Trace(sql);
int rowAffected = db.ExecuteNonQuery(sql, entity); // Dapper
return rowAffected; }
4. 查询
{
if (entity == null)
return null;
db = GetDataBase(db);
EntityDefinition definition = EntityDefinition.GetEntityDefinition(entity.GetType());
IList< string> changed = null;
if (entity != null && entity.ChangedProperties.Count > 0)
changed = entity.ChangedProperties; // 拼接查询条件的属性
string sql = string.Empty;
if (! string.IsNullOrEmpty( orderby))
orderby = " order by " + orderby;
if (changed != null && changed.Count > 0)
{ // 动态拼接查询条件
StringBuilder where = new StringBuilder();
foreach (var propertyName in changed)
{
where.AppendFormat(" {0}=@{0} and", propertyName);
}
where.Length = where.Length - 4;
sql = string.Format("select {0} from {1} where{2}{3}", definition.GetSelectCommand(), definition.TableName, where, orderby);
}
else
{ // 生成查询SQL
sql = string.Format("select {0} from {1}{2}", definition.GetSelectCommand(), definition.TableName, orderby);
}
Trace(sql);
IEnumerable<T> rows = db.ExecuteQuery<T>(sql, entity);
return rows;
}