为什么使用Delegate.Combine需要强制，但使用+运算符不？

问题描述

我找不到在反射器+操作下代表或 MulticastDelegate 。

I couldn't find the + operator in Reflector under Delegate or MulticastDelegate.

我试图找出如何，这并不需要一个转换：

I'm trying to figure out how this doesn't need a cast:

Action a = () => Console.WriteLine("A");
Action b = () => Console.WriteLine("B");

Action c = a + b;

但这：

But this does:

Action a = () => Console.WriteLine("A");
Action b = () => Console.WriteLine("B");

Action c = (Action)MulticastDelegate.Combine(a, b);

在第一个样品只是在幕后做演员？

In the first sample is the cast just done under the covers?

推荐答案

考虑下面的例子：

class Program
{
    static void Main(string[] args)
    {
        Test1();
        Test2();
    }

    public static void Test1()
    {
        Action a = () => Console.WriteLine("A");
        Action b = () => Console.WriteLine("B");

        Action c = a + b;
        c();
    }

    public static void Test2()
    {
        Action a = () => Console.WriteLine("A");
        Action b = () => Console.WriteLine("B");

        Action c = (Action)MulticastDelegate.Combine(a, b);
        c();
    }
}

然后用ILSpy看着它：

Then looking at it with ILSpy:

internal class Program
{
    private static void Main(string[] args)
    {
        Program.Test1();
        Program.Test2();
    }
    public static void Test1()
    {
        Action a = delegate
        {
            Console.WriteLine("A");
        };
        Action b = delegate
        {
            Console.WriteLine("B");
        };
        Action c = (Action)Delegate.Combine(a, b);
        c();
    }
    public static void Test2()
    {
        Action a = delegate
        {
            Console.WriteLine("A");
        };
        Action b = delegate
        {
            Console.WriteLine("B");
        };
        Action c = (Action)Delegate.Combine(a, b);
        c();
    }
}

似乎他们做同样的事情，只是C＃是提供在第一次测试的一些语法糖。

Seems that they do the exact same thing, just C# is providing some syntactic sugar in the first test.

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