如何在32位平台上pinvoke到GetWindowLongPtr和SetWindowLongPtr？

[DllImport("user32.dll", EntryPoint = "GetWindowLong")]
private static extern IntPtr GetWindowLongPtr32(IntPtr hWnd, int nIndex);

[DllImport("user32.dll", EntryPoint = "SetWindowLong")]
private static extern IntPtr SetWindowLongPtr32(IntPtr hWnd, int nIndex, IntPtr dwNewLong);

private delegate int IntPtrToInt32(IntPtr intPtr);

public static IntPtr GetWindowLongPtr(IntPtr hWnd, int nIndex)
{
    if (IntPtr.Size == 8) // 64位平台
    {
        return GetWindowLongPtr64(hWnd, nIndex);
    }
    else // 32位平台
    {
        return GetWindowLongPtr32(hWnd, nIndex);
    }
}

public static IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr dwNewLong)
{
    if (IntPtr.Size == 8) // 64位平台
    {
        return SetWindowLongPtr64(hWnd, nIndex, dwNewLong);
    }
    else // 32位平台
    {
        return SetWindowLongPtr32(hWnd, nIndex, dwNewLong);
    }
}

public static void Main(string[] args)
{
    IntPtr hWnd = new IntPtr(0x12345678);
    int nIndex = -12;
    IntPtr dwNewLong = new IntPtr(0x87654321);

    IntPtr result1 = GetWindowLongPtr(hWnd, nIndex);
    Console.WriteLine("GetWindowLongPtr result: " + result1);

    IntPtr result2 = SetWindowLongPtr(hWnd, nIndex, dwNewLong);
    Console.WriteLine("SetWindowLongPtr result: " + result2);
}