addressof-operator in c#

In a winapi function I have to p开发者_如何学Cass the address of the callback function that function has to use.

So I declared a unsafe class and everything, but bool* addressofmyfunction = &GetHandle; just won't compile!

Please help me or give me an alternative to passing the address like this.

In .NET delegates are used to store pointers to functions. For example if you have the following function:

public int GetHandle(int arg1)
{ 
    return arg1 + 10;
}

it's address will be defined like so:

Func<int, int> addressOfMyFunction = GetHandle;

and you can invoke it like that:

int result = addressOfMyFunction(50);

bool* addressofmyfunction = &GetHandle won't compile in C or C++ either (the correct syntax would be bool (*addressofmyfunction)() = &GetHandle), but you can't do like that. I'm not an expert in interop, but I think you have to use Marshal.GetFunctionPointerForDelegate.

Function pointers are represented by delegates in C#. Since methods aren't moved by the garbage collector, you don't need to pin them (or use unsafe code) to pass them to a Win32 API function.

Example:

using System;
using System.Runtime.InteropServices;

public delegate bool CallBack(int hwnd, int lParam);

public class EnumReportApp {

    [DllImport("user32")]
    public static extern int EnumWindows(CallBack x, int y); 

    public static void Main() 
    {
        CallBack myCallBack = new CallBack(EnumReportApp.Report);
        EnumWindows(myCallBack, 0);
    }

   public static bool Report(int hwnd, int lParam) { 
        Console.Write("Window handle is ");
        Console.WriteLine(hwnd);
        return true;
    }
}

There is a similar example for EnumThreadWindows on pinvoke.net.