C#中的方法组是什么? [英] What is a method group in C#?

问题描述

我经常遇到诸如无法从'方法组'转换为'字符串'"之类的错误，例如:

I have often encountered an error such as "cannot convert from 'method group' to 'string'" in cases like:

var list = new List<string>();
// ... snip
list.Add(someObject.ToString);

当然最后一行有错别字，因为我忘记了ToString后面的调用括号.正确的形式是:

of course there was a typo in the last line because I forgot the invocation parentheses after ToString. The correct form would be:

var list = new List<string>();
// ... snip
list.Add(someObject.ToString()); // <- notice the parentheses

然而我开始想知道什么是方法组.Google 并没有多大帮助，MSDN.

However I came to wonder what is a method group. Google isn't much of a help nor MSDN.

推荐答案

方法组是一组方法(可能只有一个)的名称——即理论上ToString 方法可能有多个重载(加上任何扩展方法):ToString()、ToString(string format) 等 - 因此 ToString 本身就是一个方法组".

A method group is the name for a set of methods (that might be just one) - i.e. in theory the ToString method may have multiple overloads (plus any extension methods): ToString(), ToString(string format), etc - hence ToString by itself is a "method group".

它通常可以通过使用重载解析将方法组转换为(类型化的)委托——但不能转换为字符串等；没有意义.

It can usually convert a method group to a (typed) delegate by using overload resolution - but not to a string etc; it doesn't make sense.

再次添加括号后；重载决议开始，您已经明确地识别出一个方法调用.

Once you add parentheses, again; overload resolution kicks in and you have unambiguously identified a method call.

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