C# 只能运行一个WinForm进程

using System;

using System.Collections.Generic;

using System.Linq;

using System.Windows.Forms;

using System.Diagnostics;

using System.Runtime.InteropServices;

using System.Reflection;

 

namespace OnlyProcess

{

    static class Program

    {

        [STAThread]

        static void Main()

        {

            MessageBox.Show("ddddd");

            Process instance = RunningInstance();

            if (instance == null)

            {

                System.Windows.Forms.Application.EnableVisualStyles();    //这两行可以让窗体具有XP风格.

                System.Windows.Forms.Application.DoEvents();

                Application.Run(new Form1());

            }

            else

            {

                HandleRunningInstance(instance);

            }

        }

 

        #region   只运行一个实例

        public static Process RunningInstance()

        {

            Process current = Process.GetCurrentProcess();//当前新启动的线程

            Process[] processes = Process.GetProcessesByName(current.ProcessName);

            //遍历与当前进程名称相同的进程列表

            foreach (Process process in processes)

            {

                //process,原来旧的线程与当前新启动的线程ID不一样

                //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;//返回原来旧线程的窗体

                    }

                }

            }

            return null;

        }

        private static void HandleRunningInstance(Process instance)

        {

            MessageBox.Show("该应用系统已经在运行！", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Information);

            ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL); //调用api函数，正常显示窗口

            SetForegroundWindow(instance.MainWindowHandle); //将窗口放置最前端。

        }

        [DllImport("User32.dll")]

        private static extern bool ShowWindowAsync(System.IntPtr hWnd, int cmdShow);

        [DllImport("User32.dll")]

        private static extern bool SetForegroundWindow(System.IntPtr hWnd);

        private const int WS_SHOWNORMAL = 1;

        #endregion

    }

}