Hi,

I want to marshal the following C++ struct to a managed callback
function:

struct CALLBACK_DATA
{
   LPBYTE    pArray;       // byte array
   UINT         uArrayLen;  // byte count
};

The C++ function expects the following callback type:

typedef BOOL (CALLBACK *CALLBACK_FUNC)(const CALLBACK_DATA *pData,
LPVOID pvParam);

In C# first I import the C++ function:

[DllImport("unmanaged.dll", EntryPoint = "Func")]
static extern bool Func(CallbackFunc callback, IntPtr param);

Where CallbackFunc is declared as a delegate:

public delegate bool CallbackFunc(CallbackData data, IntPtr param);

Then I define the callback and do the call:

// the callback function
public static bool Callback(CallbackData data, IntPtr param)
{
}

CallbackFunc callback = new CallbackFunc(Callback);
Func(callback, param);

The question is how do I have to declare CallbackData?

[StructLayout(LayoutKind.Sequential)]
public class CallbackData
{
   [MarshalAs(UnmanagedType.ByValArray, SizeConst=100)]  // error!
   byte[] array;
   uint    arrayLen;
}

I cannot find attibutes that fit for this situation.
Anyway the array is not const size!

Can anybody help?

Thanks,
Gernot