定义一个lambda函数并立即执行 [英] Define a lambda function and execute it immediately

问题描述

我正在定义一个lambda并通过立即附加()"来调用它.

I'm defining a lambda and calling it, by appending "()", immediately.

尝试:

int i = (() => 0) ();

错误:

错误CS0119:表达式表示预期为anonymous method', where a方法组'

那是为什么?

推荐答案

lambda只是不支持被执行.委托支持被执行. Lambda表达式可以隐式转换为委托类型.如果不要求这种转换，则不存在默认"委托类型.从.NET 2开始，我们通常将Action和Func用于所有内容，但我们可以使用不同的委托类型.

A lambda just does not support being executed. A delegate supports being executed. A lambda expression can be implicitly converted to a delegate type. In case no such conversion is requested there is no "default" delegate type. Since .NET 2 we normally use Action and Func for everything but we could use different delegate types.

首先转换为委托，然后执行:

First convert to a delegate, then execute:

((Func<int>)(() => 0))()

有人可能会争辩说，如果没有其他要求，C#应该默认使用Action和Func.从C#5开始，该语言没有这样做.

One could argue that C# should default to using Action and Func if nothing else was requested. The language does not do that as of C# 5.

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