How to restrict WPF programs with specific startup parameters to only one instance

Question

public partial class App : System.Windows.Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);
        var args = e.Args;
        if(args.Length!=0)
        {
            if (args[0] == ("login"))
            {
                new LoginWindow().Show();//conduct the login procedure
            }
            if (args[0] == ("restart"))
            {
                new SmallPanelWindow(2).Show();
            }
        }
        else
        {
            Environment.SetEnvironmentVariable("WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS", "--proxy-server=\"direct://\"");
            new MainWindow().Show();//show mainwindow which is commonly used
        }
    }

How can I ensure the LoginWindow exist only one at a time when the program is called with parameter "login" for multiple times?(eg. different triggers in windows TaskScheduler call the program with "login")Also, Starting Mainwindow can't be affected.

score 1 · Accepted Answer · answered May 30 '22 at 14:31

You could use a Mutex to ensure that only a single process at a time can open the LoginWindow:

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    var args = e.Args;
    if (args.Length!=0)
    {
        if (args[0] == ("login"))
        {
            using (Mutex mutex = new Mutex(false, "8da112cb-a833-4c50-be53-79f31b2135ca"))
            {
                if (mutex.WaitOne(0, false))
                {
                    new LoginWindow().ShowDialog(); //conduct the login procedure
                }
                else
                {
                    Environment.Exit(0);
                }
            }
        }
        if (args[0] == ("restart"))
        {
            new SmallPanelWindow(2).Show();
        }
    }
    else
    {
        Environment.SetEnvironmentVariable("WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS", "--proxy-server=\"direct://\"");
        new MainWindow().Show();//show mainwindow which is commonly used
    }
}

You may want to to move the initialization of the SmallPanelWindow inside the using statement depending on your requirements but the above sample code should give you the idea.

How to restrict WPF programs with specific startup parameters to only one instance

1 Answers1