在lambda表达式的C＃开关 [英] C# switch in lambda expression

问题描述

是否有可能已经哈在lambda表达式的开关？如果不是，为什么？ ReSharper的显示它为错误。

Is it possible to ha ve a switch in a lambda expression ? IF not, why ? Resharper display it as an error.

推荐答案

您可以在一个语句块的lambda：

You can in a statement block lambda:

Action<int> action = x =>
{
  switch(x)
  {
    case 0: Console.WriteLine("0"); break;
    default: Console.WriteLine("Not 0"); break;
  }
};

但你不能做在一个单一的lambda表达式，所以这是无效的：

But you can't do it in a "single expression lambda", so this is invalid:

// This won't work
Expression<Func<int, int>> action = x =>
  switch(x)
  {
    case 0: return 0;
    default: return x + 1;
  };

这意味着你不能在一个表达式树使用开关（至少由C＃编译器生成;我相信.NET 4.0至少已经在库中提供支持）

This means you can't use switch in an expression tree (at least as generated by the C# compiler; I believe .NET 4.0 at least has support for it in the libraries).

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