传递选择器函数时,OrderBy不会转换为SQL
当我执行:
var t = db.Table1.OrderBy(x => x.Name).ToList();
在SQL事件探查器中,这是已翻译的SQL:
SELECT [Extent1].[ID] AS [ID], [Extent1].[Name] AS [Name] FROM [dbo].[Table1] AS [Extent1] ORDER BY [Extent1].[Name] ASC
哪个是对的。
但是,如果我将选择器函数传递给OrderBy:
Func f = x => x.Name; var t = db.Table1.OrderBy(f).ToList();
翻译的SQL是:
SELECT [Extent1].[ID] AS [ID], [Extent1].[Name] AS [Name] FROM [dbo].[Table1] AS [Extent1]
orderby完全没有翻译。
有什么问题? 它们是相同的lambda函数,唯一的区别在于第二种情况,它首先被赋值给一个变量。
在IQueryable世界中,你需要一个Expression
作为OrderBy的扩展参数,而不是Func
http://msdn.microsoft.com/en-us/library/system.linq.queryable.orderby