Question

I am trying to port C++ code to C#. The code is meant to register a window class using RegisterClassEx.

The C++ code has an object WNDCLASSEX wcex. Object wcex has a property

wcex.cbSize = sizeof(WNDCLASSEX);

In C#, I have defined the structure as

    [StructLayout(LayoutKind.Sequential)]
    public struct WNDCLASSEX
    {
        public uint cbSize;
        public uint style;
        [MarshalAs(UnmanagedType.FunctionPtr)]
        public PlatformInvokeGDI32.WNDPROC lpfnWndProc;
        public int cbClsExtra;
        public int cbWndExtra;
        public IntPtr hInstance;
        public IntPtr hIcon;
        public IntPtr hCursor;
        public IntPtr hbrBackground;
        public string lpszMenuName;
        public string lpszClassName;
        public IntPtr hIconSm;
    }

I have tried to get the size using

wcex.cbSize = (uint)sizeof(WNDCLASSEX);

The function containing this stament is declared as

unsafe private void

I hoped the unsafe would make the statment work. However, I get this error in the IDE:

Cannot take the address of, get the size of, or declare a pointer to a managed type ('CaptureScreen.PlatformInvokeGDI32.WNDCLASSEX')

Can I make the structure into an unmanaged structure? If so, how?
Is there a way to use sizeof without making the structure unmanaged?
Is there a .NET version of sizeof that would work?

Answer 1

Use Marshal.SizeOf instead.