How to avoid multiple application instances?

Question

I have an application, "myprogram.exe", which calls functions and code inside a dll, one of this functions that "myprogram.exe" calls create a new instance of a winform, "MyForm.cs" and then show it using form.show();.

I can have 'n' number of "myprogram.exe" instances running, but I want to have only one instance of "MyForm.cs" for each instance of "myprogram.exe".

The problem that I have is that even thought I'm using mutex inside "MyForm.cs" to create a mutex and them ask if an instance of it is already running, sometimes, it creates another instance, despite the mutex.

Is there another way that I can use to validate if an instance of "myprogram.exe" has already created an instance of "MyForm.cs".

See http://stackoverflow.com/questions/229565/what-is-a-good-pattern-for-using-a-global-mutex-in-c/229567 and http://stackoverflow.com/questions/819773/run-single-instance-of-an-application-using-mutex — Noldorin, Jun 18 '09 at 23:10
I'd guess you're doing something wrong with the mutex; generally speaking, there would be Serious Problems if mutexes weren't doing their job. — Joe, Jun 19 '09 at 02:04
This might be a good reference: http://stackoverflow.com/questions/975250/reliably-detecting-that-another-of-my-applications-is-running — Colin Pickard, Jun 19 '09 at 09:39

score 4 · Accepted Answer · edited May 23 '17 at 12:06

As per @Joe's comment, the problem is likely to be in the implementation of the Mutux.

This answer to another question demonstrates the right way to do it:

K. Scott Allen has a good write up on using a Mutex for this purpose and issues you'll run into with the GC.
If I want to have only one instance of the application running across all sessions on the machine, I can put the named mutex into the global namespace with the prefix “Global\”.
[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());
   }
}

Thanks. I was about to post a similar question and I found this answer extremely helpful!! — bdhar, Apr 30 '10 at 09:11

score 1 · Answer 2 · answered Apr 13 '10 at 10:11

1

I post below link, since I could not find any related article in C++ and MFC. Therefore, For C++, MFC and Win32 you can use http://flounder.com/nomultiples.htm

answered Apr 13 '10 at 10:11

baris.aydinoz

1,902
2
18
28

How to avoid multiple application instances?

2 Answers2