有实际开发中，我们经常需要保持同一时间内只能运行一个实例，本文以用二个例子来演示，如何在.net下面实该功能。 

实例 一：

//方法一：只禁止多个进程运行

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

namespace DuoYeMianIE
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            bool ret;
            System.Threading.Mutex mutex = new System.Threading.Mutex(true, Application.ProductName, out ret);
            if (ret)
            {
                System.Windows.Forms.Application.EnableVisualStyles();   //这两行实现   XP   可视风格   
                System.Windows.Forms.Application.DoEvents();             //这两行实现   XP   可视风格   
                System.Windows.Forms.Application.Run(new LamBrowser());
                //   Main   为你程序的主窗体，如果是控制台程序不用这句   
                mutex.ReleaseMutex();
            }
            else
            {
                MessageBox.Show(null, "有一个和本程序相同的应用程序已经在运行，请不要同时运行多个本程序。\n\n这个程序即将退出。", Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Warning);
                //   提示信息，可以删除。   
                Application.Exit();//退出程序   
            }
        }
    }
}

实例二

//方法二：禁止多个进程运行,并当重复运行时激活以前的进程

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Reflection;

namespace DuoYeMianIE
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
{
    //Get   the   running   instance.   
    Process instance = RunningInstance();
    if (instance == null)
    { System.Windows.Forms.Application.EnableVisualStyles();   //这两行实现   XP   可视风格   
        System.Windows.Forms.Application.DoEvents();
        //There   isn't   another   instance,   show   our   form.   
        System.Windows.Forms.Application.Run(new LamBrowser());
    }    
    else
    {
        //There   is   another   instance   of   this   process.   
        HandleRunningInstance(instance);
    }
}

   
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.   
                return process;
            }
        }
    }
    //No   other   instance   was   found,   return   null. 
    return null;
}
public static void HandleRunningInstance(Process instance)
{
    //Make   sure   the   window   is   not   minimized   or   maximized   
    ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL);
    //Set   the   real   intance   to   foreground   window
    SetForegroundWindow(instance.MainWindowHandle);
}
[DllImport("User32.dll")]
private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
[DllImport("User32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);
private const int WS_SHOWNORMAL = 1;
    }
}

本文作者： 快乐家++ 原文地址：http://www.cnblogs.com/chengulv/p/3789838.html