创建单例winform应用程序

方法1：

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

  static class Program
    {
        private static Mutex singleton;
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            bool   has=Check() ;
            if (has)
            {
                Form form = new Form1();
                form.FormClosed += new FormClosedEventHandler(form_FormClosed);
                Application.Run(form);
            }
            else {
                MessageBox.Show("程序已启动");
           
            }
        }

        static void form_FormClosed(object sender, FormClosedEventArgs e)
        {
            if (singleton != null) {
                singleton.Close();
            }
        }
        private static bool Check() {
          bool   has=false;
            singleton=new   Mutex(false,Assembly.GetExecutingAssembly().FullName,out has);
         //   Assembly.GetExecutingAssembly().GetModules()[0].FullyQualifiedName;
            return has;
        }
    }
}

方法2：

    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Process instance = RunningInstance();  //Get   the   running   instance. 
            if (instance == null)
            {
                //There   isn 't   another   instance,   show   our   form. 
                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);
                Application.Run(new MainForm());
            }
            else
            {
                Message.WriteErrMsg("程序已运行，请勿再次运行!");
            }
        }
        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)
            {
                //忽略当前进程<strong> </strong>
                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;
        }
    }

方法1：不能避免多用户时的情况，多用户登陆系统时，还是可以开启多个实例的。

方法2：检查系统进程，可以解决多用户的问题，推荐方法2.