C# winform判断自身程序是否已运行，如果已运行则激活窗体

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;namespace WindowsFormsApp1
{internal static class Program{[DllImport("user32.dll")]public static extern void SwitchToThisWindow(IntPtr hWnd, bool fAltTab);/// <summary>/// 应用程序的主入口点。/// </summary>[STAThread]static void Main(){Process currentProcess = Process.GetCurrentProcess();Process[] processes = Process.GetProcessesByName(currentProcess.ProcessName);if (processes.Length > 1){//MessageBox.Show("此软件已经在运行！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);IntPtr handle = GetOldProcess(processes, currentProcess).MainWindowHandle;SwitchToThisWindow(handle, true);    // 激活，显示在最前  Thread.Sleep(1000);Environment.Exit(1);}Application.EnableVisualStyles();Application.SetCompatibleTextRenderingDefault(false);Application.Run(new Form1());}/// <summary>/// 获取老的进程/// </summary>/// <param name="processes"></param>/// <returns></returns>private static Process GetOldProcess(Process[] processes, Process currentProcess){//遍历与当前进程名称相同的进程列表foreach (Process process in processes){//如果实例已经存在则忽略当前进程if (process.Id != currentProcess.Id){//返回已经存在的进程return process;}}return null;}}
}