去年,Scott Guthrie 表示 "如果你想要对执行的SQL进行绝对控制,你实际上可以覆盖LINQ to SQL使用的原始SQL",但我找不到描述可扩展性方法的文档.
我想修改以下LINQ to SQL查询:
using (NorthwindContext northwind = new NorthwindContext ()) { var q = from row in northwind.Customers let orderCount = row.Orders.Count () select new { row.ContactName, orderCount }; }
这导致以下TSQL:
SELECT [t0].[ContactName], ( SELECT COUNT(*) FROM [dbo].[Orders] AS [t1] WHERE [t1].[CustomerID] = [t0].[CustomerID] ) AS [orderCount] FROM [dbo].[Customers] AS [t0]
至:
using (NorthwindContext northwind = new NorthwindContext ()) { var q = from row in northwind.Customers.With ( TableHint.NoLock, TableHint.Index (0)) let orderCount = row.Orders.With ( TableHint.HoldLock).Count () select new { row.ContactName, orderCount }; }
这将导致以下TSQL:
SELECT [t0].[ContactName], ( SELECT COUNT(*) FROM [dbo].[Orders] AS [t1] WITH (HOLDLOCK) WHERE [t1].[CustomerID] = [t0].[CustomerID] ) AS [orderCount] FROM [dbo].[Customers] AS [t0] WITH (NOLOCK, INDEX(0))
使用:
public static Table<TEntity> With<TEntity> ( this Table<TEntity> table, params TableHint[] args) where TEntity : class { //TODO: implement return table; } public static EntitySet<TEntity> With<TEntity> ( this EntitySet<TEntity> entitySet, params TableHint[] args) where TEntity : class { //TODO: implement return entitySet; }
和
public class TableHint { //TODO: implement public static TableHint NoLock; public static TableHint HoldLock; public static TableHint Index (int id) { return null; } public static TableHint Index (string name) { return null; } }
使用某种类型的LINQ到SQL的可扩展性,比其他的这一个.有任何想法吗?
更改底层提供程序并因此修改SQL的能力并未在LINQ to SQL中进行最终切割.
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