Program.cs

using System;
using System.Windows.Forms;
using System.Threading;
using System.Runtime.InteropServices;

namespace iMon.XBMC
{
    static class Program
    {
        static Mutex mutex = new Mutex(true, Application.ProductName);

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            try
            {
                if (mutex.WaitOne(TimeSpan.Zero, true))
                {
                    Application.EnableVisualStyles();
                    Application.SetCompatibleTextRenderingDefault(false);
                    Application.Run(new XBMC());

                    mutex.ReleaseMutex();
                }
                else
                {
                    // send our Win32 message to make the currently running instance
                    // jump on top of all the other windows
                    NativeMethods.PostMessage((IntPtr)NativeMethods.HWND_BROADCAST, NativeMethods.WM_SHOWME, IntPtr.Zero, IntPtr.Zero);
                }
            }
            catch (Exception ex)
            {
                Logging.Error("Unhandled exception", ex);

                MessageBox.Show("An unhandled exception has occured." + Environment.NewLine +
                                "Please check the debug/error log for more details", "Unhandled Exception",
                                MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        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);
        }
    }
}