去年,Scott Guthrie
stated“如果您希望绝对控制执行的sql,您实际上可以覆盖LINQ to sql使用的原始sql”,但是我找不到描述可扩展性方法的文档.
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; } }