转：限制应用程序运行一次并激活已经运行的程序 .

转载自：http://blog.csdn.net/zhxingway/article/details/5288662

C#单实例运行实现
在某些情况我们要求应用程序只能运行一次，后运行的实例要把之前运行的程序激活并自己退出。
现在是代码,找了好久哦,大家给点掌声吧,呵呵 .
关键词:winform限制主程序运行一次,激活程序,我是直接把我项目中Program.cs中的代码Copy过来了,希望大家不要见怪.

    static class Program
    {
        // Uses to active the exist window
        [DllImport("User32.dll")]
        public static extern void SetForegroundWindow(IntPtr hwnd);
        [DllImport("User32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        // 0-Hidden, 1-Centered, 2-Minimized, 3-Maximized
        private const int WS_SHOWNORMAL = 1;
        
        /// <summary>
        /// 应用程序的主入口点。
         /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            //限制程序只打开一次
              if (RunningInstance() == null)
            {
                Application.Run(new Form1());
            }
            //Application.Run(new RecordQuery());
        }

        /// <summary>
        /// 限制程序只打开一次
         /// </summary>
        /// <returns></returns>
        public static Process RunningInstance() 
        { 
            Process current = Process.GetCurrentProcess(); 
            Process[] processes = Process.GetProcessesByName(current.ProcessName); 
            //Loop through the running processes in with the same name 
            foreach (Process process in processes) 
            { 
                //Ignore the current process 
                if (process.Id != current.Id) 
                { 
                    //Make sure that the process is running from the exe file. 
                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "//") == current.MainModule.FileName) 
                    { 
                        //Return the other process instance. 
                        ShowWindowAsync(process.MainWindowHandle, WS_SHOWNORMAL);
                        SetForegroundWindow(process.MainWindowHandle);
                        return process; 
                    } 
                } 
            } 
            //No other instance was found, return null. 
            return null; 
        } 
    }