WinForms - Use Mutex to Ensure Only One Instance

The following code enforces that only one instance of your WinForms application runs at every time:

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
   try
   {
       // this is true only if the namedMutex created newly in the context of the current application
       bool namedMutexCreated = false;

       using (Mutex mtex = new Mutex(true, "BeaconClientService", out namedMutexCreated))
       {
           if (namedMutexCreated)
           {
               Application.EnableVisualStyles();
               Application.SetCompatibleTextRenderingDefault(false);
               Application.Run(new Form1());

               // when the form is closed, the mutext is released
               mtex.ReleaseMutex();
           }
           else
           {
               MessageBox.Show("An instance of Beacon Client Service is already running.", "Service Is Running", MessageBoxButtons.OK, MessageBoxIcon.Error);
           }
       }
   }
   catch (Exception ex)
   {               
       MessageBox.Show("An error occured when running the Beacon Client Service, message: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
   }
 
}

More:

• http://msdn.microsoft.com/en-us/library/system.threading.mutex.aspx