<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="https://stackoverflow.com/questions/19147/what-is-the-correct-way-to-create-a-single-instance-application">What is the correct way to create a single instance application?</a>  </p>
</blockquote>



<p>How to force C# .net app to run only one instance in Windows?</p>

I prefer a mutex solution similar to the following.  As this way it re-focuses on the app if it is already loaded
```
```
using System.Threading;

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool SetForegroundWindow(IntPtr hWnd);

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
   bool createdNew = true;
   using (Mutex mutex = new Mutex(true, "MyApplicationName", out createdNew))
   {
      if (createdNew)
      {
         Application.EnableVisualStyles();
         Application.SetCompatibleTextRenderingDefault(false);
         Application.Run(new MainForm());
      }
      else
      {
         Process current = Process.GetCurrentProcess();
         foreach (Process process in Process.GetProcessesByName(current.ProcessName))
         {
            if (process.Id != current.Id)
            {
               SetForegroundWindow(process.MainWindowHandle);
               break;
            }
         }
      }
   }
}
```
```