作者：郑佐
时间：2006-7-2

概述
本文是针对《基于.Net平台应用程序唯一运行实例实现》的补充，文章给出功能实现代码，其中SingleInstance类实现只允许一个实例运行，Program为测试主程序入口。在代码中标识说明文字。完整代码下载。

主要代码
SingleInstance.cs文件，

using System;
using System.IO;
using System.Diagnostics;
using System.Threading;
using System.Reflection;
using System.Runtime.InteropServices;
/*------------------------------------------------
郑佐 2006-07-01  http://blog.csdn.net/zhzuo     
--------------------------------------------------*/
namespace Zhengzuo.CSharpCode
{
    /// <summary>
    /// 只启动一个应用程序实例控制类
    /// </summary>
    public static class SingleInstance
    {
        private const int WS_SHOWNORMAL = 1;
        [DllImport("User32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        [DllImport("User32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        //标志文件名称
        private static string runFlagFullname = null;
        //声明同步基元
        private static Mutex mutex = null; 
 
        /// <summary>
        /// static Constructor
        /// </summary>
        static SingleInstance()
        {
        } 

        #region api实现     
        /// <summary>
        /// 获取应用程序进程实例,如果没有匹配进程，返回Null
        /// </summary>
        /// <returns>返回当前Process实例</returns>
        public static Process GetRunningInstance()
        {           

            Process currentProcess = Process.GetCurrentProcess();//获取当前进程
            //获取当前运行程序完全限定名
            string currentFileName = currentProcess.MainModule.FileName;
            //获取进程名为ProcessName的Process数组。
            Process[] processes = Process.GetProcessesByName(currentProcess.ProcessName);
            //遍历有相同进程名称正在运行的进程
            foreach (Process process in processes)
            {
                if (process.MainModule.FileName == currentFileName)
                {
                    if (process.Id != currentProcess.Id)//根据进程ID排除当前进程
                        return process;//返回已运行的进程实例
                }
            }
            return null;
        } 

        /// <summary>
        /// 获取应用程序句柄，设置应用程序前台运行，并返回bool值
        /// </summary>
        public static bool HandleRunningInstance(Process instance)
        {
            //确保窗口没有被最小化或最大化
            ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL);
            //设置真实例程为foreground window
            return SetForegroundWindow(instance.MainWindowHandle);
        } 

        /// <summary>
        /// 获取窗口句柄，设置应用程序前台运行，并返回bool值，重载方法
        /// </summary>
        /// <returns></returns>
        public static bool HandleRunningInstance()
        {
            Process p = GetRunningInstance();
            if (p != null)
            {
                HandleRunningInstance(p);
                return true;
            }
            return false;
        } 

        #endregion

        #region Mutex实现
        /// <summary>
        /// 创建应用程序进程Mutex
        /// </summary>
        /// <returns>返回创建结果，true表示创建成功，false创建失败。</returns>
        public static bool CreateMutex()
        {
            return CreateMutex(Assembly.GetEntryAssembly().FullName);
        } 

        /// <summary>
        /// 创建应用程序进程Mutex
        /// </summary>
        /// <param name="name">Mutex名称</param>
        /// <returns>返回创建结果，true表示创建成功，false创建失败。</returns>
        public static bool CreateMutex(string name)
        {
            bool result = false;
            mutex = new Mutex(true, name, out result);
            return result; 
        } 

        /// <summary>
        /// 释放Mutex
        /// </summary>
        public static void ReleaseMutex()
        {
            if (mutex != null)
            {
                mutex.Close();
            }
        } 

        #endregion

        #region 设置标志实现
        /// <summary>
        /// 初始化程序运行标志，如果设置成功，返回true，已经设置返回false，设置失败将抛出异常
        /// </summary>
        /// <returns>返回设置结果</returns>
        public static bool InitRunFlag()
        {
            if (File.Exists(RunFlag))
            {
                return false;
            }
            using (FileStream fs = new FileStream(RunFlag, FileMode.Create))
            {
            }
            return true;
        } 

        /// <summary>
        /// 释放初始化程序运行标志，如果释放失败将抛出异常
        /// </summary>
        public static void DisposeRunFlag()
        {
            if (File.Exists(RunFlag))
            {
                File.Delete(RunFlag);
            }
        } 

            get
            {
                if(runFlagFullname == null)
                {
                    string assemblyFullName = Assembly.GetEntryAssembly().FullName;
                    //CommonApplicationData：//"C:\\Documents and Settings\\All Users\\Application Data"
                    string path = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);
                    //"C:\\Program Files\\Common Files"
                    //string path = Environment.GetFolderPath(Environment.SpecialFolder.CommonProgramFiles);
                    runFlagFullname = Path.Combine(path, assemblyFullName);
                }
                return runFlagFullname;
            }
            set
            {
                runFlagFullname = value;
            }
        }
        #endregion
    }

}

Program.cs文件，

using System;
using System.Windows.Forms;
using System.Diagnostics;
using Zhengzuo.CSharpCode;
/*------------------------------------------------
  郑佐 2006-07-01  http://blog.csdn.net/zhzuo
--------------------------------------------------*/
namespace Zhengzuo.Test.WinGui
{
    static class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            if (args.Length == 0) //没有传送参数
            {
                Process p = SingleInstance.GetRunningInstance();
                if (p != null) //已经有应用程序副本执行
                {
                    SingleInstance.HandleRunningInstance(p);
                }
                else //启动第一个应用程序
                {
                    RunApplication();
                }
            }
            else //有多个参数
            {
                switch (args[0].ToLower())
                {
                    case "-api":
                        if (SingleInstance.HandleRunningInstance() == false)
                        {
                            RunApplication();
                        }
                        break;
                    case "-mutex":
                        if (args.Length >= 2) //参数中传入互斥体名称
                        {
                            if ( SingleInstance.CreateMutex(args[1]) )
                            {
                                RunApplication();
                                SingleInstance.ReleaseMutex();
                            }
                            else
                            {
                                //调用SingleInstance.HandleRunningInstance()方法显示到前台。
                                MessageBox.Show("程序已经运行！");
                            }
                        }
                        else
                        {
                            if (SingleInstance.CreateMutex())
                            {
                                RunApplication();
                                SingleInstance.ReleaseMutex();
                            }
                            else
                            {
                                //调用SingleInstance.HandleRunningInstance()方法显示到前台。
                                MessageBox.Show("程序已经运行！");
                            }
                        }
                        break;
                    case "-flag"://使用该方式需要在程序退出时调用
                        if (args.Length >= 2) //参数中传入运行标志文件名称
                        {
                            SingleInstance.RunFlag = args[1];                         
                        }
                        try
                        {
                            if (SingleInstance.InitRunFlag())
                            {
                                RunApplication();
                                SingleInstance.DisposeRunFlag();
                            }
                            else
                            {
                                //调用SingleInstance.HandleRunningInstance()方法显示到前台。
                                MessageBox.Show("程序已经运行！");
                            }
                        }
                        catch (Exception ex)
                        {
                            MessageBox.Show(ex.ToString());
                        }
                        break;
                    default:
                        MessageBox.Show("应用程序参数设置失败。");
                        break;
                }
            }
        } 

        //启动应用程序
        static void RunApplication()
        {
            Application.EnableVisualStyles();
            Application.Run(new MainForm());
        }
    }
}

运行CMD命令行，
第一种调用方式：
WindowsApplication1.exe
或 WindowsApplication1.exe –api
第二种调用方式：
WindowsApplication1.exe –mutex
或WindowsApplication1.exe –mutex {F140AE26-626C-42f8-BD49-45025742205E}
第三种调用方式：
WindowsApplication1.exe –flag
或WindowsApplication1.exe –flag c:\blog.csdn.net.zhzuo

针对远程访问的测试，需要在系统管理工具的.NET Framework 2.0 Configuration中进行设置授权该局域网路径允许访问，否则会抛出System.Security.SecurityException异常。
根据测试结果可见三种实现方式适用范围不同，理想的实现是结合他们的优点进行多点判断。