How to wrap the capSetCallbackXXXXXX function

I try the following code:

public delegate Int32 capErrorCallback(IntPtr hWnd, Int32 nID,
[MarshalAs(UnmanagedType.LPWStr)]
String lpsz);

public static Boolean capSetCallbackOnError(IntPtr hwnd, capErrorCallback errorCallback)
{
return AVICapSendMessage(hwnd, WM_CAP_SET_CALLBACK_ERRORW, 0,
(Int32)errorCallback.Method.MethodHandle.Value) == 0 false : true;
}

but the code looks doesn't work, the error cause a NullReferenceException. I am not sure which cause the problem. Could anybody give any advice

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How to wrap the capSetCallbackXXXXXX function

Alan1203
Maybe the usage of errorCallback.Method.MethodHandle.Value isn't correct or something else
Lee Meyers
I try my code in VS 2005, the exception is more specific-it's AccessViolationException, but i don't know which cause the exception, managed code or unmanaged.:(
Kapil Singhal
I solved this problem by using the new GetFunctionPointerForDelegate function in .NET 2.0.

public static Boolean capSetCallbackOnError(IntPtr hwnd, capErrorCallback errorCallback)
{
IntPtr ad = Marshal.GetFunctionPointerForDelegate(errorCallback);

return AVICapSendMessage(hwnd, WM_CAP_SET_CALLBACK_ERRORW, 0,
(Int32)ad) == 0 false : true;
}
How to wrap the capSetCallbackXXXXXX function

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