如何將Linq擴展到SQL？

去年，斯科特·格思裏stated「實際上，你可以重寫，如果你想在執行的SQL絕對控制是LINQ to SQL中使用原始SQL」，但我不能找到一種描述方法，擴展文件。如何將Linq擴展到SQL？

我想修改下面的LINQ to SQL查詢：

using (NorthwindContext northwind = new NorthwindContext()) { 
    var q = from row in northwind.Customers 
      let orderCount = row.Orders.Count() 
      select new { 
       row.ContactName, 
       orderCount 
      }; 
}

導致下面的TSQL：

SELECT [t0].[ContactName], (
    SELECT COUNT(*) 
    FROM [dbo].[Orders] AS [t1] 
    WHERE [t1].[CustomerID] = [t0].[CustomerID] 
    ) AS [orderCount] 
FROM [dbo].[Customers] AS [t0]

要：

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 
      }; 
}

其中會導致以下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; 
}

而且

 
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; 
    } 
}

使用到SQL擴展某些類型的LINQ，比this one等。有任何想法嗎？

來源

2008-09-15 George Tsiokos