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步步为营VS 2008 + .NET 3.5(13) - DLINQ(LINQ to SQL)之用户自定义函数、在不同的DataContext之间做更新、缓存、获取信息、数据加载选项和延迟加载
作者：webabcd
介绍
以Northwind为示例数据库，DLINQ(LINQ to SQL)之调用标量值用户自定义函数；调用表值用户自定义函数；使用数据加载选项加载数据；相关信息的获取；字段的延迟加载；在不同的DataContext之间做更新；缓存
示例
Others.aspx.cs
using System;using System.Data;using System.Configuration;using System.Collections;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using System.Xml.Linq;using DAL;public partial class LINQ_DLINQ_Others : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
// 调用标量值用户自定义函数 Call_HelloFunctionScalar(); // 调用表值用户自定义函数 Call_HelloFunctionTable(); // 不使用数据加载选项 DataLoadOptions_Original(); // 使用数据加载选项加载数据 DataLoadOptions_LoadWith(); // 使用数据加载选项加载数据，并且限制所要加载的数据 DataLoadOptions_AssociateWith(); // 相关信息的获取 GetInfo(); // 字段的延迟加载 DelayLoaded(); // 在不同的DataContext之间做更新 IsVersion(); // 缓存 ShowCache();
}
}调用标量值用户自定义函数
ALTER FUNCTION dbo.fnHelloFunctionScalar( @param nvarchar(100))RETURNS nvarchar(200)ASBEGIN RETURN 'Hello:' + @param END /// <summary> /// 调用标量值用户自定义函数 /// </summary> void Call_HelloFunctionScalar() { NorthwindDataContext ctx = new NorthwindDataContext(); result.InnerHtml += ctx.HelloFunctionScalar("webabcd"); result.InnerHtml += "<br />"; result.InnerHtml += "<br />"; }Hello:webabcd
调用表值用户自定义函数
ALTER FUNCTION dbo.fnHelloFunctionTable( @ID int, @name nvarchar(100))RETURNS @tbl TABLE ([ID] int, [Name] nvarchar(100))ASBEGIN INSERT INTO @tbl VALUES (@ID, @name) RETURN END /// <summary> /// 调用表值用户自定义函数 /// </summary> void Call_HelloFunctionTable() { NorthwindDataContext ctx = new NorthwindDataContext(); var p = (ctx.HelloFunctionTable(1, "webabcd")).Single(); result.InnerHtml += "ID：" + p.ID; result.InnerHtml += "<br />"; result.InnerHtml += "Name：" + p.Name; result.InnerHtml += "<br />"; result.InnerHtml += "<br />"; }ID：1
Name：webabcd
不使用数据加载选项
/// <summary> /// 不使用数据加载选项 /// </summary> void DataLoadOptions_Original() { NorthwindDataContext ctx = new NorthwindDataContext(); var categories = from c in ctx.Categories select c; foreach (var c in categories) { // 每一次迭代都会执行一条SQL语句来返回当前Category的Product foreach (var p in c.Products) { string productName = p.ProductName + "<br>"; } } }//SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description], [t0].[Picture]//FROM [dbo].[Categories] AS [t0]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [1]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [2]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [3]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [4]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [5]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [6]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [7]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued]//FROM [dbo].[Products] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [8]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1使用数据加载选项加载数据
/// <summary> /// 使用数据加载选项加载数据 /// </summary> void DataLoadOptions_LoadWith() { NorthwindDataContext ctx = new NorthwindDataContext(); System.Data.Linq.DataLoadOptions options = new System.Data.Linq.DataLoadOptions(); // Category以LEFT JOIN的方式关联Product options.LoadWith<Categories>(c => c.Products); ctx.LoadOptions = options; var categories = from c in ctx.Categories select c; foreach (var c in categories) { foreach (var p in c.Products) { string productName = p.ProductName + "<br>"; } } }//SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description], [t0].[Picture], [t1].[ProductID], [t1].[ProductName], [t1].[SupplierID], [t1].[CategoryID] AS [CategoryID2], [t1].[QuantityPerUnit], [t1].[UnitPrice], [t1].[UnitsInStock], [t1].[UnitsOnOrder], [t1].[ReorderLevel], [t1].[Discontinued], (// SELECT COUNT(*)// FROM [dbo].[Products] AS [t2]// WHERE [t2].[CategoryID] = [t0].[CategoryID]// ) AS [count]//FROM [dbo].[Categories] AS [t0]//LEFT OUTER JOIN [dbo].[Products] AS [t1] ON [t1].[CategoryID] = [t0].[CategoryID]//ORDER BY [t0].[CategoryID], [t1].[ProductID]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1使用数据加载选项加载数据，并且限制所要加载的数据
/// <summary> /// 使用数据加载选项加载数据，并且限制所要加载的数据 /// </summary> void DataLoadOptions_AssociateWith() { NorthwindDataContext ctx = new NorthwindDataContext(); System.Data.Linq.DataLoadOptions options = new System.Data.Linq.DataLoadOptions(); // Category以LEFT JOIN的方式关联Product options.LoadWith<Categories>(c => c.Products); // 限制所关联的Product options.AssociateWith<Categories>(c => c.Products.Where(p => p.UnitPrice > 20)); ctx.LoadOptions = options; var categories = from c in ctx.Categories select c; foreach (var c in categories) { foreach (var p in c.Products) { string productName = p.ProductName + "<br>"; } } }//SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description], [t0].[Picture], [t1].[ProductID], [t1].[ProductName], [t1].[SupplierID], [t1].[CategoryID] AS [CategoryID2], [t1].[QuantityPerUnit], [t1].[UnitPrice], [t1].[UnitsInStock], [t1].[UnitsOnOrder], [t1].[ReorderLevel], [t1].[Discontinued], (// SELECT COUNT(*)// FROM [dbo].[Products] AS [t2]// WHERE ([t2].[UnitPrice] > @p0) AND ([t2].[CategoryID] = [t0].[CategoryID])// ) AS [count]//FROM [dbo].[Categories] AS [t0]//LEFT OUTER JOIN [dbo].[Products] AS [t1] ON ([t1].[UnitPrice] > @p0) AND ([t1].[CategoryID] = [t0].[CategoryID])//ORDER BY [t0].[CategoryID], [t1].[ProductID]//-- @p0: Input Currency (Size = 0; Prec = 19; Scale = 4) [20]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1相关信息的获取
/// <summary> /// 相关信息的获取 /// </summary> void GetInfo() { NorthwindDataContext ctx = new NorthwindDataContext(); var categories = from c in ctx.Categories select c; result.InnerHtml += "ProviderType：" + ctx.Mapping.ProviderType.ToString() + "<br />"; result.InnerHtml += "DatabaseName：" + ctx.Mapping.DatabaseName + "<br />"; result.InnerHtml += "ContextType：" + ctx.Mapping.ContextType.ToString() + "<br />"; result.InnerHtml += "TableName：" + ctx.Mapping.GetTable(typeof(Categories)).TableName + "<br />"; result.InnerHtml += "Expression：" + categories.Expression.ToString() + "<br />"; result.InnerHtml += "T-SQL：" + categories.Provider.ToString() + "<br />"; }ProviderType：System.Data.Linq.SqlClient.SqlProvider
DatabaseName：C:\DOCUMENTS AND SETTINGS\WANGLEI\桌面\VS2008\WEB\APP_DATA\NORTHWIND.MDF
ContextType：DAL.NorthwindDataContext
TableName：dbo.Categories
Expression：Table(Categories).Select(c => c)
T-SQL：SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description] FROM [dbo].[Categories] AS [t0]
字段的延迟加载
/// <summary> /// 字段的延迟加载 /// </summary> void DelayLoaded() { // 在对象关系设计器（Object Relational Designer）中设置Categories实体的Picture属性的Delay Loaded为True NorthwindDataContext ctx = new NorthwindDataContext(); var category = (from c in ctx.Categories select c).Single(c => c.CategoryID == 1); System.Data.Linq.Binary b = category.Picture; }//SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description]//FROM [dbo].[Categories] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [1]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1//SELECT [t0].[Picture]//FROM [dbo].[Categories] AS [t0]//WHERE [t0].[CategoryID] = @p0//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [1]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1在不同的DataContext之间做更新
/// <summary> /// 在不同的DataContext之间做更新 /// </summary> void IsVersion() { // 在Categories实体的主键上添加属性IsVersion=true，即Time Stamp为True Categories c = null; using (NorthwindDataContext ctx = new NorthwindDataContext()) { ctx.DeferredLoadingEnabled = false; c = ctx.Categories.First(); c.Description = "webabcd"; } using (NorthwindDataContext ctx = new NorthwindDataContext()) { ctx.Categories.Attach(c, true); ctx.SubmitChanges(); } }//UPDATE [dbo].[Categories]//SET [CategoryName] = @p2, [Description] = @p3//WHERE ([CategoryID] = @p0) AND ([CategoryID] = @p1)//-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [1]//-- @p1: Input Int32 (Size = 0; Prec = 0; Scale = 0) [1]//-- @p2: Input String (Size = 9; Prec = 0; Scale = 0) [Beverages]//-- @p3: Input String (Size = 7; Prec = 0; Scale = 0) [webabcd]//-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1缓存
/// <summary> /// 缓存 /// </summary> void ShowCache() { // 查询后数据会被缓存，如果之后以主键查询的话，会先在缓存里查找 NorthwindDataContext ctx = new NorthwindDataContext(); Categories category = ctx.Categories.Single(c => c.CategoryName == "Beverages"); Categories category2 = ctx.Categories.Single(c => c.CategoryName == "Beverages"); Categories category3 = ctx.Categories.Single(c => c.CategoryID == 1); Categories category4 = ctx.Categories.Single(c => c.CategoryID == 1); Categories category5 = ctx.Categories.Single(c => c.CategoryID == 2); Categories category6 = ctx.Categories.Single(c => c.CategoryID == 2); }SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description]FROM [dbo].[Categories] AS [t0]WHERE [t0].[CategoryName] = @p0-- @p0: Input String (Size = 9; Prec = 0; Scale = 0) [Beverages]-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description]FROM [dbo].[Categories] AS [t0]WHERE [t0].[CategoryName] = @p0-- @p0: Input String (Size = 9; Prec = 0; Scale = 0) [Beverages]-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1SELECT [t0].[CategoryID], [t0].[CategoryName], [t0].[Description]FROM [dbo].[Categories] AS [t0]WHERE [t0].[CategoryID] = @p0-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [2]-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1OK
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