static class Program     {         /// <summary>         /// The main entry point for the application.         /// </summary>         [STAThread]         static void Main()         {             bool createdNew;             //系统能够识别有名称的互斥，因此可以使用它禁止应用程序启动两次             //第二个参数可以设置为产品的名称:Application.ProductName             //每次启动应用程序，都会验证名称为SingletonWinAppMutex的互斥是否存在             Mutex mutex = new Mutex(false, "SingletonWinAppMutex", out createdNew);             //如果已运行，则在前端显示             //createdNew == false，说明程序已运行             if (!createdNew)             {                 Process instance = GetExistProcess();                 if (instance != null)                 {                     SetForegroud(instance);                     Application.Exit();                     return;                 }             }             Application.EnableVisualStyles();             Application.SetCompatibleTextRenderingDefault(false);             Application.Run(new MainForm());         }         /// <summary>         /// 查看程序是否已经运行         /// </summary>         /// <returns></returns>         private static Process GetExistProcess()         {             Process currentProcess = Process.GetCurrentProcess();             foreach (Process process in Process.GetProcessesByName(currentProcess.ProcessName))             {                 if ((process.Id != currentProcess.Id) &&                     (Assembly.GetExecutingAssembly().Location == currentProcess.MainModule.FileName))                 {                     return process;                 }             }             return null;         }         /// <summary>         /// 使程序前端显示         /// </summary>         /// <param name="instance"></param>         private static void SetForegroud(Process instance)         {             IntPtr mainFormHandle = instance.MainWindowHandle;             if (mainFormHandle != IntPtr.Zero)             {                 ShowWindowAsync(mainFormHandle, 1);                 SetForegroundWindow(mainFormHandle);             }         }         [DllImport("User32.dll")]         private static extern bool SetForegroundWindow(IntPtr hWnd);         [DllImport("User32.dll")]         private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);     }