using System; using System.Collections.Generic; using System.Linq; using System.Threading; using System.Threading.Tasks; using System.Windows.Forms; namespace WindowsFormsApplication3 { static class Program { /// <summary> /// The main entry point for the application. /// </summary> [STAThread] static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); const string appName = "WindowsFormsApplication3"; bool createdNew; Mutex mut = new Mutex(true, appName, out createdNew); if (!createdNew) { MessageBox.Show($"WindowsFormsApplication3 is already running!", "Multiple Instances"); return; } Application.Run(new Form1()); } } } b