How can global function exist in C#?

问题

How can global function exist in C# when everything is defined inside a class? I was reading the documentation of OpCodes.Call at MSDN, and was surprised to see the following wordings,

The metadata token carries sufficient information to determine whether the call is to a static method, an instance method, a virtual method, or a global function.

Global function? Does it exist in C#? (It definitely doesn't refer to static method, as it's explicitly listed along with global function).

回答1:

You can't have global functions in C#, it's just not part of the language. You have to use a static method on some class of your choosing to get similar functionality.

However C# is not the only language that uses the CLR. One can write Managed C++, which can have global functions.

回答2:

At the Build 2014 conference it was announced that from Roslyn onwards, you can import static methods from types by the using TypeName; directive, so that instead of having to use System.Math.Min(...) you can do:

using System.Math;
...
var z = Min(x,y);

Note: by the time of release this became:

using static System.Math;

回答3:

Because System.Reflection.Emit.OpCodes.Call isn't about C#. It's about emitting IL opcodes. In IL, there are features that are not available in C#. Global functions is one of those features.

回答4:

I suppose that the thing is, that this is IL injection operation, but IL is not absolutely only about C#. In other words it's for support of the language that supports global functions.

回答5:

The documentation you are referring to is for .net. C# does not cater for global functions but .net does.

回答6:

C# does not support all features of MSIL. Global functions is one of them. VB.Net, F#, IronPython or some other language likley to use this and other features that are not generated by C# compiler.

回答7:

I'm just overwriting my previous answer...

Here is what each look like in IL DASM with their associated codes:

// Static Method
IL_0001:  call       void testapp.Form1::Test()

// Instance Method
IL_0001:  call       instance void testapp.Form1::Test()

// Virtual Method
IL_0001:  callvirt   instance void testapp.Form1::Test()

// Global Function
IL_0000:  call       void testapp.Test()

So to answer your question, there isn't a direct way to generate the metadata token in the last method for C#. I had to create the last in C++.

来源：https://stackoverflow.com/questions/7296106/how-can-global-function-exist-in-c

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