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再接再厉VS 2008 sp1 + .NET 3.5 sp1(4) - Entity Framework(实体框架)之EntityClient, ObjectQuery
作者:webabcd
介绍
以Northwind为示例数据库,ADO.NET Entity Framework之详解EntityClient, ObjectQuery
- EntityConnection - 与存储模型的连接
- EntityCommand - 对 EDM 执行的命令
- EntityParameter - 配置 EntityCommand 的参数
- EntityDataReader - 以只读、只进的数据流的方式获取数据(内存中始终只有一行)。相当于SqlDataReader
- ObjectQuery<T> - 通过 Entity SQL 或 查询语法 或 Linq 方法对概念模型做查询
- ObjectContext.CreateQuery<T>(Entity SQL) - 根据 esql 创建一个 ObjectQuery<T> 。(延迟)
示例
1、关于EntityClient
EntityClient.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Data.EntityClient;
using System.Data;
using VS2008SP1.Business;
public partial class EntityFramework_EntityClient : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
Demo();
result.InnerHtml += "<br />";
Demo2();
result.InnerHtml += "<br />";
Demo3();
}
}
void Demo()
{
string strConn = System.Configuration.ConfigurationManager.ConnectionStrings["NorthwindEntities"].ConnectionString;
// EntityConnection - 与存储模型的连接。构造函数的参数为连接字符串
// Open() - 打开连接
// Close() - 关闭连接
// CreateCommand() - 创建此连接的 EntityCommand 对象
using (EntityConnection conn = new EntityConnection(strConn))
{
conn.Open();
try
{
// EntityCommand - 对 EDM 执行的命令
// CommandType - 命令类型 [System.Data.CommandType枚举]
// CommandType.Text - esql语句。默认值
// CommandType.StoredProcedure - 存储过程名
// CommandType.TableDirect - 表名
// CommandText - 命令文本。esql语句或存储过程名或表名
// CommandTimeout - 超时时间。单位:秒
using (EntityCommand cmd = conn.CreateCommand())
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select value c from NorthwindEntities.Categories as c";
// EntityDataReader - 以只读、只进的数据流的方式获取数据(内存中始终只有一行)。相当于SqlDataReader
// Read() - 读下一条记录
// HasRows() - 是否还有可读数据
// Close() - 关闭 EntityDataReader
// EntityCommand.ExecuteReader() - 执行命令,返回 EntityDataReader 对象
using (EntityDataReader edr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (edr.Read())
{
result.InnerHtml += edr["CategoryName"].ToString() + "<br />";
}
}
}
}
catch (Exception ex)
{
result.InnerHtml += ex.ToString();
}
finally
{
conn.Close();
}
}
/*
SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
*/
}
void Demo2()
{
// EntityConnection 构造函数的参数为 name = web.config中的connectionStrings中配置的连接字符串的name
using (EntityConnection conn = new EntityConnection("name = NorthwindEntities"))
{
conn.Open();
try
{
using (EntityCommand cmd = conn.CreateCommand())
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select value s from NorthwindEntities.categories as s where s.categoryId = @categoryId";
// EntityParameter - 配置 EntityCommand 的参数
// ParameterName - 参数名
// Value- 参数值
// Size - 参数大小
// DbTyp - 参数类型 [System.Data.DbType 枚举]
// IsNullable - 是否接受 null 值
EntityParameter param = new EntityParameter();
param.ParameterName = "categoryId";
param.Value = 1;
// EntityCommand.Parameters.Add() - 为 EntityCommand 增加参数
cmd.Parameters.Add(param);
using (EntityDataReader edr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (edr.Read())
{
result.InnerHtml += edr.GetString(1) + "<br />";
}
}
}
}
catch (Exception ex)
{
result.InnerHtml += ex.ToString();
}
finally
{
conn.Close();
}
}
/*
exec sp_executesql N'SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
WHERE [Extent1].[CategoryID] = @categoryId',N'@categoryId int',@categoryId=1
*/
}
void Demo3()
{
// EntityConnectionStringBuilder - 构造连接字符串
EntityConnectionStringBuilder entityBuilder = new EntityConnectionStringBuilder();
entityBuilder.Provider = "System.Data.SqlClient";
entityBuilder.ProviderConnectionString = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Northwind.mdf;Integrated Security=True;User Instance=True;MultipleActiveResultSets=True";
entityBuilder.Metadata = @"res://*/Northwind.csdl|res://*/Northwind.ssdl|res://*/Northwind.msl";
using (EntityConnection conn = new EntityConnection(entityBuilder.ConnectionString))
{
conn.Open();
try
{
using (EntityCommand cmd = conn.CreateCommand())
{
// 调用存储过程(需要先做好映射,然后指定概念模型中的函数名称)
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "NorthwindEntities.GetCategory";
EntityParameter param = new EntityParameter();
param.ParameterName = "CategoryID";
param.Value = 1;
cmd.Parameters.Add(param);
using (EntityDataReader edr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (edr.Read())
{
result.InnerHtml += edr["CategoryName"].ToString() + "<br />";
}
}
}
}
catch (Exception ex)
{
result.InnerHtml += ex.ToString();
}
finally
{
conn.Close();
}
}
/*
exec [dbo].[spSelectCategory] @CategoryID=1
*/
}
}
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Data.EntityClient;
using System.Data;
using VS2008SP1.Business;
public partial class EntityFramework_EntityClient : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
Demo();
result.InnerHtml += "<br />";
Demo2();
result.InnerHtml += "<br />";
Demo3();
}
}
void Demo()
{
string strConn = System.Configuration.ConfigurationManager.ConnectionStrings["NorthwindEntities"].ConnectionString;
// EntityConnection - 与存储模型的连接。构造函数的参数为连接字符串
// Open() - 打开连接
// Close() - 关闭连接
// CreateCommand() - 创建此连接的 EntityCommand 对象
using (EntityConnection conn = new EntityConnection(strConn))
{
conn.Open();
try
{
// EntityCommand - 对 EDM 执行的命令
// CommandType - 命令类型 [System.Data.CommandType枚举]
// CommandType.Text - esql语句。默认值
// CommandType.StoredProcedure - 存储过程名
// CommandType.TableDirect - 表名
// CommandText - 命令文本。esql语句或存储过程名或表名
// CommandTimeout - 超时时间。单位:秒
using (EntityCommand cmd = conn.CreateCommand())
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select value c from NorthwindEntities.Categories as c";
// EntityDataReader - 以只读、只进的数据流的方式获取数据(内存中始终只有一行)。相当于SqlDataReader
// Read() - 读下一条记录
// HasRows() - 是否还有可读数据
// Close() - 关闭 EntityDataReader
// EntityCommand.ExecuteReader() - 执行命令,返回 EntityDataReader 对象
using (EntityDataReader edr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (edr.Read())
{
result.InnerHtml += edr["CategoryName"].ToString() + "<br />";
}
}
}
}
catch (Exception ex)
{
result.InnerHtml += ex.ToString();
}
finally
{
conn.Close();
}
}
/*
SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
*/
}
void Demo2()
{
// EntityConnection 构造函数的参数为 name = web.config中的connectionStrings中配置的连接字符串的name
using (EntityConnection conn = new EntityConnection("name = NorthwindEntities"))
{
conn.Open();
try
{
using (EntityCommand cmd = conn.CreateCommand())
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select value s from NorthwindEntities.categories as s where s.categoryId = @categoryId";
// EntityParameter - 配置 EntityCommand 的参数
// ParameterName - 参数名
// Value- 参数值
// Size - 参数大小
// DbTyp - 参数类型 [System.Data.DbType 枚举]
// IsNullable - 是否接受 null 值
EntityParameter param = new EntityParameter();
param.ParameterName = "categoryId";
param.Value = 1;
// EntityCommand.Parameters.Add() - 为 EntityCommand 增加参数
cmd.Parameters.Add(param);
using (EntityDataReader edr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (edr.Read())
{
result.InnerHtml += edr.GetString(1) + "<br />";
}
}
}
}
catch (Exception ex)
{
result.InnerHtml += ex.ToString();
}
finally
{
conn.Close();
}
}
/*
exec sp_executesql N'SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
WHERE [Extent1].[CategoryID] = @categoryId',N'@categoryId int',@categoryId=1
*/
}
void Demo3()
{
// EntityConnectionStringBuilder - 构造连接字符串
EntityConnectionStringBuilder entityBuilder = new EntityConnectionStringBuilder();
entityBuilder.Provider = "System.Data.SqlClient";
entityBuilder.ProviderConnectionString = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Northwind.mdf;Integrated Security=True;User Instance=True;MultipleActiveResultSets=True";
entityBuilder.Metadata = @"res://*/Northwind.csdl|res://*/Northwind.ssdl|res://*/Northwind.msl";
using (EntityConnection conn = new EntityConnection(entityBuilder.ConnectionString))
{
conn.Open();
try
{
using (EntityCommand cmd = conn.CreateCommand())
{
// 调用存储过程(需要先做好映射,然后指定概念模型中的函数名称)
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "NorthwindEntities.GetCategory";
EntityParameter param = new EntityParameter();
param.ParameterName = "CategoryID";
param.Value = 1;
cmd.Parameters.Add(param);
using (EntityDataReader edr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (edr.Read())
{
result.InnerHtml += edr["CategoryName"].ToString() + "<br />";
}
}
}
}
catch (Exception ex)
{
result.InnerHtml += ex.ToString();
}
finally
{
conn.Close();
}
}
/*
exec [dbo].[spSelectCategory] @CategoryID=1
*/
}
}
2、关于ObjectQuery
ObjectQuery.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Data.EntityClient;
using System.Data;
using System.Data.Common;
using VS2008SP1.Business;
public partial class EntityFramework_ObjectQuery : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
Demo();
result.InnerHtml += "<br />";
Demo2();
result.InnerHtml += "<br />";
Demo3();
result.InnerHtml += "<br />";
Demo4();
}
}
private void Demo()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select value c from NorthwindEntities.Categories as c";
// ObjectQuery<T> - 通过 Entity SQL 或 查询语法 或 Linq 方法对概念模型做查询
// ObjectContext.CreateQuery<T>(Entity SQL) - 根据 esql 创建一个 ObjectQuery<T> 。(延迟)
ObjectQuery<Categories> query = ctx.CreateQuery<Categories>(esql);
foreach (var c in query)
{
result.InnerHtml += c.CategoryName + "<br />";
}
}
/*
SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
*/
}
private void Demo2()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select c.CategoryName from NorthwindEntities.Categories as c";
// ObjectQuery<T>()构造函数 - 根据 esql 创建一个 ObjectQuery ,返回 DbDataRecord 。(延迟)
// System.Data.Objects.MergeOption枚举 - 如何将此次查询结果与之前同一 ObjectContext 的存在与内存的查询结果做合并
// MergeOption.AppendOnly - 追加。默认值
// MergeOption.OverwriteChanges - 以新结果为准
// MergeOption.PreserveChanges - 以原结果为准
// MergeOption.NoTracking - 取消变更跟踪,不会使用 ObjectStateManager,减少执行查询的时间,所有返回的实体将是分离的状态(detached state)
ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esql, ctx, MergeOption.NoTracking);
// 可以在 ObjectQuery<T> 上使用 Linq 方法或查询语法
foreach (DbDataRecord item in query.Take(3))
{
result.InnerHtml += item["CategoryName"].ToString() + "<br />";
}
}
/*
SELECT
[Limit1].[C1] AS [C1],
[Limit1].[CategoryName] AS [CategoryName]
FROM ( SELECT TOP (3)
[Extent1].[CategoryName] AS [CategoryName],
1 AS [C1]
FROM [dbo].[Categories] AS [Extent1]
) AS [Limit1]
*/
}
private void Demo3()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select value count(c.CategoryID) from NorthwindEntities.Categories as c";
// ObjectQuery<简单类型> 的示例(延迟)
ObjectQuery<int> query = ctx.CreateQuery<int>(esql);
result.InnerHtml += query.First().ToString() + "<br />";
}
/*
SELECT
[Limit1].[A1] AS [C1]
FROM ( SELECT TOP (1)
COUNT([Extent1].[CategoryID]) AS [A1]
FROM [dbo].[Categories] AS [Extent1]
) AS [Limit1]
*/
}
private void Demo4()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select value c from NorthwindEntities.Categories as c";
// 延迟
ObjectQuery<Categories> query = ctx.CreateQuery<Categories>(esql);
// ObjectQuery<T>.Execute() - 立即执行查询。返回 ObjectResult<T>
ObjectResult<Categories> queryResult = query.Execute(MergeOption.NoTracking);
foreach (var c in queryResult)
{
result.InnerHtml += c.CategoryName + "<br />";
}
}
/*
SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
*/
}
}
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Data.EntityClient;
using System.Data;
using System.Data.Common;
using VS2008SP1.Business;
public partial class EntityFramework_ObjectQuery : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
Demo();
result.InnerHtml += "<br />";
Demo2();
result.InnerHtml += "<br />";
Demo3();
result.InnerHtml += "<br />";
Demo4();
}
}
private void Demo()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select value c from NorthwindEntities.Categories as c";
// ObjectQuery<T> - 通过 Entity SQL 或 查询语法 或 Linq 方法对概念模型做查询
// ObjectContext.CreateQuery<T>(Entity SQL) - 根据 esql 创建一个 ObjectQuery<T> 。(延迟)
ObjectQuery<Categories> query = ctx.CreateQuery<Categories>(esql);
foreach (var c in query)
{
result.InnerHtml += c.CategoryName + "<br />";
}
}
/*
SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
*/
}
private void Demo2()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select c.CategoryName from NorthwindEntities.Categories as c";
// ObjectQuery<T>()构造函数 - 根据 esql 创建一个 ObjectQuery ,返回 DbDataRecord 。(延迟)
// System.Data.Objects.MergeOption枚举 - 如何将此次查询结果与之前同一 ObjectContext 的存在与内存的查询结果做合并
// MergeOption.AppendOnly - 追加。默认值
// MergeOption.OverwriteChanges - 以新结果为准
// MergeOption.PreserveChanges - 以原结果为准
// MergeOption.NoTracking - 取消变更跟踪,不会使用 ObjectStateManager,减少执行查询的时间,所有返回的实体将是分离的状态(detached state)
ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esql, ctx, MergeOption.NoTracking);
// 可以在 ObjectQuery<T> 上使用 Linq 方法或查询语法
foreach (DbDataRecord item in query.Take(3))
{
result.InnerHtml += item["CategoryName"].ToString() + "<br />";
}
}
/*
SELECT
[Limit1].[C1] AS [C1],
[Limit1].[CategoryName] AS [CategoryName]
FROM ( SELECT TOP (3)
[Extent1].[CategoryName] AS [CategoryName],
1 AS [C1]
FROM [dbo].[Categories] AS [Extent1]
) AS [Limit1]
*/
}
private void Demo3()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select value count(c.CategoryID) from NorthwindEntities.Categories as c";
// ObjectQuery<简单类型> 的示例(延迟)
ObjectQuery<int> query = ctx.CreateQuery<int>(esql);
result.InnerHtml += query.First().ToString() + "<br />";
}
/*
SELECT
[Limit1].[A1] AS [C1]
FROM ( SELECT TOP (1)
COUNT([Extent1].[CategoryID]) AS [A1]
FROM [dbo].[Categories] AS [Extent1]
) AS [Limit1]
*/
}
private void Demo4()
{
using (var ctx = new NorthwindEntities())
{
string esql = "select value c from NorthwindEntities.Categories as c";
// 延迟
ObjectQuery<Categories> query = ctx.CreateQuery<Categories>(esql);
// ObjectQuery<T>.Execute() - 立即执行查询。返回 ObjectResult<T>
ObjectResult<Categories> queryResult = query.Execute(MergeOption.NoTracking);
foreach (var c in queryResult)
{
result.InnerHtml += c.CategoryName + "<br />";
}
}
/*
SELECT
[Extent1].[CategoryID] AS [CategoryID],
[Extent1].[CategoryName] AS [CategoryName],
[Extent1].[Description] AS [Description],
[Extent1].[Picture] AS [Picture]
FROM [dbo].[Categories] AS [Extent1]
*/
}
}
OK
[源码下载]