Question

In .NET, how can I prevent multiple instances of an app from running at the same time and what caveats should I consider if there are multiple ways to do it?

Answer 1

Use Mutex. One of the examples above using GetProcessByName has many caveats. Here is a good article on the subject:

https://web.archive.org/web/20230610150623/https://odetocode.com/blogs/scott/archive/2004/08/20/the-misunderstood-mutex.aspx

[STAThread] static void Main()  {    using(Mutex mutex = new Mutex(false, "Global\\" + appGuid))    {       if(!mutex.WaitOne(0, false))       {          MessageBox.Show("Instance already running");          return;       }           Application.Run(new Form1());    } }  private static string appGuid = "c0a76b5a-12ab-45c5-b9d9-d693faa6e7b9";