using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Runtime.InteropServices;
namespace DrawTest {
    class Program {

        [DllImport("user32.dll", EntryPoint = "GetDesktopWindow")]
        static extern IntPtr GetDesktopWindow ();

        [DllImport("User32.dll")]
        static extern IntPtr GetDC ( IntPtr hwnd );

        [DllImport("User32.dll")]
        static extern void ReleaseDC ( IntPtr dc );

        static void Main ( string[] args ) {
            while( true ) {
                IntPtr desktop = GetDC(GetDesktopWindow());
                using( Graphics g = Graphics.FromHdc(desktop) ) {
                    g.FillRectangle(Brushes.White, 0, 0, 100, 100);
                    System.Threading.Thread.Sleep(10);
                }
                ReleaseDC(desktop);
            }
            System.Console.ReadLine();
        }
    }
}