保证Winform程序只有一个实例在运行

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Windows.Forms;

namespace Terry{
    class Program
    {
        private Mutex mutex = null;

        public Program()
        {
            mutex = new Mutex(false, "TerrySoft_MUTEX");
            if (!mutex.WaitOne(0, false))
            {
                mutex.Close();
                mutex = null;
            }
        }

        public void ReleaseMutex()
        {
            if (mutex != null)
            {
                mutex.ReleaseMutex();
                mutex = null;
            }
        }

        ~Program()
        {
            ReleaseMutex();
        }

                /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {

            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            Program cm = new Program();
            if (cm.mutex == null)
            {
                MessageBox.Show("已经有一个程序在运行中。");
            }
            else
            {
                Application.Run(new frmStart());
            }
            cm.ReleaseMutex();//手工释放Mutex

        }

    }
}