Func键<>&GT表达℃之间的差异;和Func键<> [英] Difference between Expression<Func<>> and Func<>

问题描述

作为一个例子，为什么大多数LINQ运营商接受表达式来; Func键< TSource>> 及其等价物 Func键< TSource> ？

As an example, why do most LINQ operators accept Expression<Func<TSource>> and its equivalent Func<TSource>?

有什么好处/之所以使用，而不是直线上升lambda语法的一般表达类？

What's the benefit/reason for using the generic Expression class instead of straight up lambda syntax?

推荐答案

使用表达式来; T> 你明确地创建一个< A HREF =htt​​p://msdn.microsoft.com/en-us/library/bb397951.aspx> 表达式树的 - 这意味着你可以处理，使得代码了查询，好像它是数据

Using Expression<T> you are explicitly creating an expression tree - this means that you can deal with the code that makes up the query as if it were data.

这样做的原因是，LINQ提供（如LINQ到SQL例如）检查查询本身来确定的最佳方式C＃的表达式转换成T-SQL查询。由于表达式树可以让你看看代码为数据提供者能够做到这一点。

The reason for this is that LINQ providers (like LINQ to SQL for example) inspect the query itself to determine the best way to translate the C# expressions into a T-SQL query. Since an expression tree lets you look at the code as data the provider is able to do this.

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