EF查询生成的SQL

在EF 4和EF 3.5 SP1中，我们可以使用ToTraceString()方法得到EF查询所生成的SQL。

using (var context = new TestDBEntities())
{
    var query = from p in context.Parents
                where p.Name == "zhaokun"
                select p;

    ObjectQuery<Parent> parents = query as ObjectQuery<Parent>;
    if (parents != null)
    {
        string sql = parents.ToTraceString();
    }
}

这里所生成的SQL为：

[Extent1].[ParentID] AS [ParentID], 
[Extent1].[Name] AS [Name]
FROM [dbo].[Parent] AS [Extent1]
WHERE N'zhaokun'=[Extent1].[Name]

在EF 4.1中，我们可以直接调用DbQuery<>的ToString()方法得到所生成的SQL。

using (var context = new MyDbContext())
{
    var people = from p in context.People
                 where p.PersonID > 100
                 select p;

    string sql = people.ToString();
}

所生成的SQL是：

SELECT 
[Extent1].[PersonID] AS [PersonID], 
[Extent1].[Name] AS [Name]
FROM [dbo].[People] AS [Extent1]
WHERE [Extent1].[PersonID] > 100

这里的ToString()方法其实也就是调用了ObjectQuery<>的ToTraceString()方法。 DbQuery<>.ToString() ==>  System.Data.Entity.Internal.Linq.InternalQuery<>.ToString()方法，此方法 在.NET Reflector得到的实现是这样的：

public override string ToString()
{
    return this._objectQuery.ToTraceString();
}

看书得到！