// this class just wraps some Win32 stuff that we're going to use for blocking of multiple instances using System; using System.Runtime.InteropServices; internal class NativeMethods { public const int HWND_BROADCAST = 0xffff; public static readonly int WM_SHOWME = RegisterWindowMessage("WM_SHOWME"); [DllImport("user32")] public static extern bool PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam); [DllImport("user32")] public static extern int RegisterWindowMessage(string message); }