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