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linq to entity 详解（查询）

(2011-08-17 15:09:20)

标签：

linq

to

entity

杂谈

分类： linqtoentity系列(非原创)

以Northwind为示例数据库，ADO.NET Entity Framework之Linq To Entities

Select - 选择需要返回的字段
Where - 筛选
OrderBy - 正序排序
OrderByDescending - 倒序排序
ThenBy - 在 OrderBy 或 OrderByDescending 的基础上再正序排序
ThenByDescending - 在 OrderBy 或 OrderByDescending 的基础上再倒序排序
GroupBy - 分组
Join - 连接
GroupJoin - 连接后分组

示例
Select

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // Select 对应的 Linq 方法
http://www.cnblogs.com/Images/dot.gif{ ProductName = "产品名称：" + p.ProductName });
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // Select 对应的查询语法
http://www.cnblogs.com/Images/dot.gif{ ProductName = "产品名称：" + p.ProductName };
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--Select 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif1 AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gifN'产品名称：' + [Extent1].[ProductName] AS [C2]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM [dbo].[Products] AS [Extent1]

Where

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // Where 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Products.Where(p => p.ProductID > 3);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // Where 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from p in ctx.Products where p.ProductID > 3 select p;
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--Where 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif1 AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[SupplierID] AS [SupplierID]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM [dbo].[Products] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifWHERE [Extent1].[ProductID] > 3

OrderBy

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // OrderBy 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Products.OrderBy(p => p.UnitPrice);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // OrderBy 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from p in ctx.Products orderby p.UnitPrice select p;
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--OrderBy 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[C1] AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[SupplierID] AS [SupplierID]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM ( SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[SupplierID] AS [SupplierID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    1 AS [C1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    FROM [dbo].[Products] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif)  AS [Project1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY [Project1].[UnitPrice] ASC

OrderByDescending

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // OrderByDescending 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Products.OrderByDescending(p => p.UnitPrice);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // OrderByDescending 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from p in ctx.Products orderby p.UnitPrice descending select p;
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--OrderByDescending 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[C1] AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[SupplierID] AS [SupplierID]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM ( SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[SupplierID] AS [SupplierID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    1 AS [C1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    FROM [dbo].[Products] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif)  AS [Project1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY [Project1].[UnitPrice] DESC

ThenBy

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // ThenBy 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Products.OrderBy(p => p.UnitPrice).ThenBy(p => p.ProductID);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // ThenBy 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from p in ctx.Products orderby p.UnitPrice ascending, p.ProductID ascending select p;
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--ThenBy 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[C1] AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[SupplierID] AS [SupplierID]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM ( SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[SupplierID] AS [SupplierID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    1 AS [C1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    FROM [dbo].[Products] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif)  AS [Project1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY [Project1].[UnitPrice] ASC, [Project1].[ProductID] ASC

ThenByDescending

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // ThenByDescending 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Products.OrderBy(p => p.UnitPrice).ThenByDescending(p => p.ProductID);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // ThenByDescending 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from p in ctx.Products orderby p.UnitPrice ascending, p.ProductID descending select p;
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--ThenByDescending 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[C1] AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[SupplierID] AS [SupplierID]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM ( SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[SupplierID] AS [SupplierID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    1 AS [C1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    FROM [dbo].[Products] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif)  AS [Project1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY [Project1].[UnitPrice] ASC, [Project1].[ProductID] DESC

GroupBy

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // GroupBy 对应的 Linq 方法
http://www.cnblogs.com/Images/dot.gif{ Group = g.Key, Member = g });
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    foreach (var g in p1)
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        // g.Group - 供货商ID，以此分组
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        // g.Member - 某供货商下的所有产品
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        foreach (var m in g.Member)
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif            // code
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif        }
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif    }
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // GroupBy 对应的查询语法
http://www.cnblogs.com/Images/dot.gif{ Group = g.Key, Member = g };
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    foreach (var g in p2)
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        // g.Group - 供货商ID，以此分组
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        // g.Member - 某供货商下的所有产品
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        foreach (var m in g.Member)
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif            // code
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif        }
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif    }
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--GroupBy 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[SupplierID] AS [SupplierID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[C1] AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[C2] AS [C2],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[C4] AS [C3],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[C3] AS [C4],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project2].[SupplierID1] AS [SupplierID1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM ( SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Distinct1].[SupplierID] AS [SupplierID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    1 AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    1 AS [C2],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE WHEN ([Extent2].[Discontinued] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C3],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[CategoryID] AS [CategoryID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[Discontinued] AS [Discontinued],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[ProductID] AS [ProductID],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[ProductName] AS [ProductName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[QuantityPerUnit] AS [QuantityPerUnit],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[ReorderLevel] AS [ReorderLevel],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[SupplierID] AS [SupplierID1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[UnitPrice] AS [UnitPrice],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[UnitsInStock] AS [UnitsInStock],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent2].[UnitsOnOrder] AS [UnitsOnOrder],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE WHEN ([Extent2].[Discontinued] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C4]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    FROM   (SELECT DISTINCT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        [Extent1].[SupplierID] AS [SupplierID]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        FROM [dbo].[Products] AS [Extent1] ) AS [Distinct1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    LEFT OUTER JOIN [dbo].[Products] AS [Extent2] ON ([Extent2].[SupplierID] = [Distinct1].[SupplierID]) OR (([Extent2].[SupplierID] IS NULL) AND ([Distinct1].[SupplierID] IS NULL))
http://www.cnblogs.com/Images/OutliningIndicators/None.gif)  AS [Project2]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY [Project2].[SupplierID] ASC, [Project2].[C4] ASC

Join

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // Join 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Products.Join(
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        ctx.Categories,
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        p => p.Categories.CategoryID,
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        c => c.CategoryID,
http://www.cnblogs.com/Images/dot.gif{ c.CategoryName, p.ProductName });
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // Join 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from p in ctx.Products
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif             join c in ctx.Categories
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif             on p.Categories.CategoryID equals c.CategoryID
http://www.cnblogs.com/Images/dot.gif{ c.CategoryName, p.ProductName };
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--Join 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif1 AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent2].[CategoryName] AS [CategoryName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Extent1].[ProductName] AS [ProductName]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM [dbo].[Products] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifINNER JOIN [dbo].[Categories] AS [Extent2] ON ([Extent1].[CategoryID] = [Extent2].[CategoryID]) OR (([Extent1].[CategoryID] IS NULL) AND ([Extent2].[CategoryID] IS NULL))

GroupJoin

http://www.cnblogs.com/Images/OutliningIndicators/None.gifusing (var ctx = new NorthwindEntities())
http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // GroupJoin 对应的 Linq 方法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p1 = ctx.Categories.GroupJoin(
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        ctx.Products,
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        c => c.CategoryID,
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif        p => p.Categories.CategoryID,
http://www.cnblogs.com/Images/dot.gif{ p.CategoryName, ProductCount = g.Count() });
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p1.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    // GroupJoin 对应的查询语法
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    var p2 = from c in ctx.Categories
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif             join p in ctx.Products
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif             on c.CategoryID equals p.Categories.CategoryID into g // g - IEnumerable<Products>
http://www.cnblogs.com/Images/dot.gif{ CategoryName = c.CategoryName, ProductCount = g.Count() };
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif    p2.ToList();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif}

http://www.cnblogs.com/Images/OutliningIndicators/None.gif--GroupJoin 对应的 sql 语句
http://www.cnblogs.com/Images/OutliningIndicators/None.gif
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif1 AS [C1],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[CategoryName] AS [CategoryName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif[Project1].[C1] AS [C2]
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM ( SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    [Extent1].[CategoryName] AS [CategoryName],
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    (SELECT
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        COUNT(cast(1 as bit)) AS [A1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        FROM [dbo].[Products] AS [Extent2]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHERE ([Extent1].[CategoryID] = [Extent2].[CategoryID]) OR (([Extent1].[CategoryID] IS NULL) AND ([Extent2].[CategoryID] IS NULL))) AS [C1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    FROM [dbo].[Categories] AS [Extent1]
http://www.cnblogs.com/Images/OutliningIndicators/None.gif)  AS [Project1]

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