using System.Runtime.InteropServices;using System.Diagnostics;using System.Reflection;//*****************************************************  static class Program    {        /// <summary>        /// 该函数设置由不同线程产生的窗口的显示状态。        /// </summary>        /// <param name="hWnd">窗口句柄</param>        /// <param name="cmdShow">指定窗口如何显示。查看允许值列表，请查阅ShowWlndow函数的说明部分。</param>        /// <returns>如果函数原来可见，返回值为非零；如果函数原来被隐藏，返回值为零。</returns>        [DllImport("User32.dll")]        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);        /// <summary>        /// 该函数将创建指定窗口的线程设置到前台，并且激活该窗口。键盘输入转向该窗口，并为用户改各种可视的记号。系统给创建前台窗口的线程分配的权限稍高于其他线程。        /// </summary>        /// <param name="hWnd">将被激活并被调入前台的窗口句柄。</param>        /// <returns>如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零。</returns>        [DllImport("User32.dll")]        private static extern bool SetForegroundWindow(IntPtr hWnd);        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);            Process instance = RunningInstance();            if (instance == null)            {                Form1 frm = new Form1();                Application.Run(new Form1());            }            else            {                HandleRunningInstance(instance);            }        }        /// <summary>        /// 获取正在运行的实例，没有运行的实例返回null;        /// </summary>        public static Process RunningInstance()        {            Process current = Process.GetCurrentProcess();            Process[] processes = Process.GetProcessesByName(current.ProcessName);            foreach (Process process in processes)            {                if (process.Id != current.Id)                {                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == current.MainModule.FileName)                    {                        return process;                    }                }            }            return null;        }        /// <summary>        /// 显示已运行的程序。        /// </summary>        public static void HandleRunningInstance(Process instance)        {            ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL); //显示，可以注释掉            SetForegroundWindow(instance.MainWindowHandle);            //放到前端        }    }

//=====创建互斥体法：=====bool blnIsRunning;Mutex mutexApp = new Mutex(false, Assembly.GetExecutingAssembly().FullName, out   blnIsRunning);if (!blnIsRunning){    MessageBox.Show("程序已经运行！", "提示",    MessageBoxButtons.OK, MessageBoxIcon.Exclamation);    return;}   //保证同时只有一个客户端在运行   System.Threading.Mutex mutexMyapplication = new System.Threading.Mutex(false, "OnePorcess.exe");if (!mutexMyapplication.WaitOne(100, false)){    MessageBox.Show("程序" + Application.ProductName + "已经运行！", Application.ProductName,    MessageBoxButtons.OK, MessageBoxIcon.Error);    return;}//=====判断进程法：(修改程序名字后依然能执行)=====Process current = Process.GetCurrentProcess();Process[] processes = Process.GetProcessesByName(current.ProcessName);foreach (Process process in processes){    if (process.Id != current.Id)    {        if (process.MainModule.FileName        == current.MainModule.FileName)        {            MessageBox.Show("程序已经运行！", Application.ProductName,            MessageBoxButtons.OK, MessageBoxIcon.Exclamation);            return;        }    }}