Prevent multiple instances of wpf application

  private void Application_Startup(object sender, StartupEventArgs e)
        {
            Process thisProc = Process.GetCurrentProcess();
            if (Process.GetProcessesByName(thisProc.ProcessName).Length > 1)
            {
                MessageBox.Show("Application running");
                Application.Current.Shutdown();
                return;
            }
 
            var wLogin = new LoginWindow();
 
            if (wLogin.ShowDialog() == true)
            {
                var wMain = new Main();
                wMain.WindowState = WindowState.Maximized;
                wMain.Show();
            }
            else
            {
                Application.Current.Shutdown();
            }      
        }