传递一个选择器功能时，排序依据是没有转化为SQL [英] OrderBy is not translated into SQL when passing a selector function

问题描述

当我执行：

var t = db.Table1.OrderBy(x => x.Name).ToList();

在SQL事件探查器，这是转换为SQL语句：

In SQL profiler, this is the translated SQL:

SELECT 
[Extent1].[ID] AS [ID], 
[Extent1].[Name] AS [Name]
FROM [dbo].[Table1] AS [Extent1]
ORDER BY [Extent1].[Name] ASC

这是正确的。

不过，如果我传递一个选择器功能来排序依据：

However, if I pass a selector function to OrderBy:

Func<Table1, string> f = x => x.Name;
var t = db.Table1.OrderBy(f).ToList();

转换为SQL语句是：

The translated SQL is:

SELECT 
[Extent1].[ID] AS [ID], 
[Extent1].[Name] AS [Name]
FROM [dbo].[Table1] AS [Extent1]

的排序依据是完全没有翻译。

The orderby is totally not translated.

这是什么问题？它们是相同的lambda函数，唯一的区别是在第二个情况下，首先分配给一个变​​量

What's the problem? They are the same lambda function, the only difference is in the 2nd case, it is first assigned to a variable.

推荐答案

原因在IQueryable的世界，你需要一个表达式来; Func键<的TModel，TValue>> 作为排序依据的扩展参数，而不是一个 Func键<的TModel，TValue> ;

Cause in a IQueryable world, you need an Expression<Func<TModel, TValue>> as the OrderBy's extension parameter, not a Func<TModel, TValue>

的 http://msdn.microsoft.com/en-us/library/system.linq.queryable.orderby

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