C＃中：是否有可能在一个匿名方法来声明一个局部变量？ [英] C#: Is it possible to declare a local variable in an anonymous method?

问题描述

时，可以在下面的代码在一个匿名的C＃方法的局部变量，即我想只执行一次计数。

Is is possible to have a local variable in an anonymous c# methods, i.e. in the following code I would like to perform the count only once.

IQueryable<Enquiry> linq = db.Enquiries;

if(...) linq = linq.Where(...);

if(...) linq = linq.Where(e => 
    (x <= (from p in db.Orders where p.EnquiryId == e.Id select p).Count() && 
        (from p in db.Orders where p.EnquiryId == e.Id select p).Count() <= y));

if(...) linq = linq.Where(...);

var result = (from e in linq select e);

有没有让匿名函数？

Is there a "let" for anonymous functions?

更新：
请注意，我添加几个凡该语句之后子句，所以我不能用一个选择关闭

Update: Note that I'm adding several Where clauses after this statement so I can't close with a select.

/尼尔斯

推荐答案

我碰到类似的问题。该解决方案是创建一个自定义表达式树生成方法。

I've run into a similar problem. The solution is to create a custom expression tree generating method.

我问在MSDN上的论坛的问题。请参阅问题和答案在这里：的重用哪里表达式。

I asked my question on MSDN-forums. Please see the question and answer here: Reusing Where expressions.

这可能给你如何进行的想法，但我必须承认，自定义表达式树木不适合胆小的人; - ）

This may give you an idea on how to proceed, but I must admit that custom expression trees are not for the faint-hearted ;-)

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