Question

I’m trying to do an interop to a C++ structure from C#. The structure (in a C# wrapper) is something like this

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
public struct SENSE4_CONTEXT
{
    public System.IntPtr dwIndex; // Or UInt64, depending on platform.
}

The underlying C++ structure is a bit abnormal. On a 32-bit OS, dwIndex must be IntPtr in order for the interop to work, but on a 64-bit OS, it must be UInt64 in order for the interop to work.

How can I modify the above structure to make it work on both a 32-bit and 64-bit OS?

Answer 1

If the “dw” prefix in dwIndex is accurate then it sounds like a DWORD, which is a 32-bit unsigned integer. In that case you need to use UIntPtr, which will be like UInt32 on 32-bit and like UInt64 on 64-bit.

It seems unlikely that your C++ program requires a signed integer on a 32-bit platform and an unsigned one on a 64-bit one (though not impossible, of course).