在 C# 中将委托强制转换为 Func [英] Cast delegate to Func in C#

问题描述

我有代码:

public delegate int SomeDelegate(int p);

public static int Inc(int p) {
    return p + 1;
}

我可以将 Inc 转换为 SomeDelegate 或 Func:

I can cast Inc to SomeDelegate or Func<int, int>:

SomeDelegate a = Inc;
Func<int, int> b = Inc;

但我不能将 Inc 转换为 SomeDelegate 并在转换为 Func<int, int> 之后使用通常的方式如下:

but I can't cast Inc to SomeDelegate and after that cast to Func<int, int> with usual way like this:

Func<int, int> c = (Func<int, int>)a; // Сompilation error

我该怎么做?

推荐答案

SomeDelegate a = Inc;
Func<int, int> b = Inc;

简称

SomeDelegate a = new SomeDelegate(Inc); // no cast here
Func<int, int> b = new Func<int, int>(Inc);

您不能将 SomeDelegate 的实例强制转换为 Func<int, int>出于同样的原因，您不能将字符串转换为 Dictionary<int, int>-- 它们是不同的类型.

You can't cast an instance of SomeDelegate to a Func<int, int> for the same reason you can't cast a string to a Dictionary<int, int> -- they're different types.

这行得通:

Func<int, int> c = x => a(x);

这是语法糖

class MyLambda
{
   SomeDelegate a;
   public MyLambda(SomeDelegate a) { this.a = a; }
   public int Invoke(int x) { return this.a(x); }
}

Func<int, int> c = new Func<int, int>(new MyLambda(a).Invoke);

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