Is there a Delegate which isn't a MulticastDelegate in C#?

I think the answer is NO? If there isn't, why do we have separated Delegate and MulticastDelegate classes? Maybe it's ag开发者_如何学运维ain because of "some other .NET languages"?

EDIT: I thought this was part of ECMA 335, but I can't see it in there anywhere.

You can't create such a delegate type in C#, but you can in IL:

.class public auto ansi sealed Foo
       extends [mscorlib]System.Delegate
{
    // Body as normal
}

The C# compiler has no problems using such a delegate:

using System;

class Test
{
    static void Main()
    {
        Foo f = x => Console.WriteLine(x);
        f("hello");
    }
}

But the CLR does when it tries to load it:

Unhandled Exception: System.TypeLoadException: Could not load type 'Foo' from assembly 'Foo, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' because it cannot inherit directly from the delegate class. at Test.Main()

Basically the Delegate/MulticastDelegate separation is an historical accident. I believe that early alpha/beta versions did make the distinction, but it proved too confusing and generally not useful - so now every delegate derives from MulticastDelegate.

(Interestingly, the C# specification only mentions MulticastDelegate once, in the list of types which can't be used as generic constraints.)

No, there isn't, because all delegates must naturally be able to be Delegate.Combineed. Delegate is there simply to wrap the non-multicasting functionality into a base class.

System.MuticastDelegate is derived from System.Delegate. Each level within the delegate hierarchy provides a different set of services. System.Delegate is a container of the data for what method to call on a particular object. With System.MulticastDelegate comes the additional capability of not only invoking a method on a single object, but on a collections of objects. This enables multiple subscribers to an event.

Not sure, i have answered your question.

No, the CLR does not allow that.

I recall something that they wanted to expose Delegate directly, but that was never needed.