public static void Register(Type t)
        {
            RegistryKey rk = Registry.LocalMachine.CreateSubKey(@"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers\" + t.Name);

            rk.SetValue(string.Empty, t.GUID.ToString("B").ToUpper());
            rk.Close();
            ShellInterop.SHChangeNotify(0x08000000, 0, IntPtr.Zero, IntPtr.Zero);
        }
 public static void Unregister(Type t)
 {
     Registry.LocalMachine.DeleteSubKeyTree(@"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers\" + t.Name);
     ShellInterop.SHChangeNotify(0x08000000, 0, IntPtr.Zero, IntPtr.Zero);
 }