C#應用程式只能開啟一次，應用程式只能開啟一個,應用程式不能重複開啟

修改program.cs中的程式 ********************************************* using System; using System.Collections.Generic; using System.Windows.Forms; using System.Threading; namespace PCBilling_Server {     static class Program     {         public static bool bOnlyOneInstance = false;         /// <summary>         /// 應用程式的主進入點。         /// </summary>         [STAThread]         static void Main()         {             bOnlyOneInstance = false;             Mutex mutex = new Mutex(true, Application.UserAppDataPath.Replace(@"/", "_"), out bOnlyOneInstance);             if (!bOnlyOneInstance)             {                 MessageBox.Show("系統已經運行!", "提示資訊", MessageBoxButtons.OK, MessageBoxIcon.Information);                 System.Environment.Exit(0);                 return;             }             Application.EnableVisualStyles();             Application.SetCompatibleTextRenderingDefault(false);             Application.Run(new Frm_Login());         }     } }