Winform防止程序重复运行

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Tool;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;

namespace 计算器
{
    static class Program
    {
        [DllImport("user32.dll")]
        public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        /// <summary>
        /// 该函数设置由不同线程产生的窗口的显示状态。
        /// </summary>
        /// <param name="hWnd">窗口句柄</param>
        /// <param name="cmdShow">指定窗口如何显示。查看允许值列表，请查阅ShowWlndow函数的说明部分。</param>
        /// <returns>如果函数原来可见，返回值为非零；如果函数原来被隐藏，返回值为零。</returns>
        [DllImport("User32.dll")]
        private static extern bool ShowWindow(IntPtr hWnd, int cmdShow);
        /// <summary>
        /// 该函数将创建指定窗口的线程设置到前台，并且激活该窗口。键盘输入转向该窗口，并为用户改各种可视的记号。系统给创建前台窗口的线程分配的权限稍高于其他线程。
        /// </summary>
        /// <param name="hWnd">将被激活并被调入前台的窗口句柄。</param>
        /// <returns>如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零。</returns>
        [DllImport("User32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        private const int SW_SHOWNORMAL = 1;

        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            Process processes = RunningInstance();
            if (processes == null)
            {
                Application.Run(new Form1());
            }
            else
            {
                HandleRunningInstance(processes);
            }
        }

        /// <summary>
        /// 获取正在运行的实例，没有运行的实例返回null;
        /// </summary>
        public static Process RunningInstance()
        {
            Process current = Process.GetCurrentProcess();
            Process[] processes = Process.GetProcessesByName(current.ProcessName);
            foreach (Process process in processes)
            {
                if (process.Id != current.Id)
                {
                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == current.MainModule.FileName)
                    {
                        return process;
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// 显示已运行的程序。
        /// </summary>
        public static void HandleRunningInstance(Process instance)
        {
            try
            {
                IntPtr formHwnd = FindWindow(null, "计算器");
                ShowWindow(formHwnd, SW_SHOWNORMAL);   //显示
                SetForegroundWindow(formHwnd);         //放到前端
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}