Run one instance from the application

Question

I have a windows application (C#) and i need to configure it to run one instance from the application at the time , It means that one user clicked the .exe file and the appl

Answer 1

I'd use a Mutex for this scenario. Alternatively, a Semaphore would also work (but a Mutex seems more apt).

Here's my example (from a WPF application, but the same principles should apply to other project types):

public partial class App : Application
{
    const string AppId = "MY APP ID FOR THE MUTEX";
    static Mutex mutex = new Mutex(false, AppId);
    static bool mutexAccessed = false;

    protected override void OnStartup(StartupEventArgs e)
    {
        try
        {
            if (mutex.WaitOne(0))
                mutexAccessed = true;
        }
        catch (AbandonedMutexException)
        {
            //handle the rare case of an abandoned mutex
            //in the case of my app this isn't a problem, and I can just continue
            mutexAccessed = true;
        }

        if (mutexAccessed)
            base.OnStartup(e);
        else
            Shutdown();
    }

    protected override void OnExit(ExitEventArgs e)
    {
        if (mutexAccessed)
            mutex?.ReleaseMutex();

        mutex?.Dispose();
        mutex = null;
        base.OnExit(e);
    }
}