using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Threading;
using System.Diagnostics;
using System.Reflection;

namespace MyClient
{
    
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            //bool blnCreate;//Another method to make sure only one instance
            //Mutex m = new Mutex(true, "MyClient", out blnCreate);
            //if (blnCreate)
            CloseRunningInstance();
            Application.Run(new MainFrm());
        }
        //Close the existed instance of my application
        static void CloseRunningInstance()
        {
            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)
                    {
                        //Close the other process instance.   
                        process.Kill();
                        process.WaitForExit();
                    }
                }
            }
        } 
    }
}

本文转自CoderZh博客园博客，原文链接：http://www.cnblogs.com/coderzh/archive/2007/12/10/989375.html，如需转载请自行联系原作者