C# WinForm 程序单实例运行，再次运行时激活前一个实例

一个简单的小程序，演示了winform程序如何运行单实例。当有实例运行时，再次单击，会激活第一个实例。

附主要源码：

Program.cs

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

namespace SingleInstance
{
    static class Program
    {
        public static EventWaitHandle ProgramStarted;

        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            // 尝试创建一个命名事件
            bool createNew;
            ProgramStarted = new EventWaitHandle(false, EventResetMode.AutoReset, "MyStartEvent", out createNew);

            // 如果该命名事件已经存在(存在有前一个运行实例)，则发事件通知并退出
            if (!createNew)
            {
                ProgramStarted.Set();
                return;
            }

            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());

        }

    }
}

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace SingleInstance
{
    public partial class Form1 : Form
    {
        NotifyIcon notifyIcon1 = new NotifyIcon();

        public Form1()
        {
            InitializeComponent();

            this.notifyIcon1.Text = "Double click to show window";
            this.notifyIcon1.Icon = System.Drawing.SystemIcons.Application;
            this.notifyIcon1.DoubleClick += OnNotifyIconDoubleClicked;
            this.SizeChanged += OnSizeChanged;
            ThreadPool.RegisterWaitForSingleObject(Program.ProgramStarted, OnProgramStarted, null, -1, false);
            this.WindowState = FormWindowState.Normal;
        }

        // 当最小化时，放到系统托盘。
        void OnSizeChanged(object sender, EventArgs e)
        {
            if (this.WindowState == FormWindowState.Minimized)
            {
                this.notifyIcon1.Visible = true;
                this.Visible = false;
            }
        }

        // 当双击托盘图标时，恢复窗口显示
        void OnNotifyIconDoubleClicked(object sender, EventArgs e)
        {
            this.Visible = true;
            this.notifyIcon1.Visible = false;
            this.WindowState = FormWindowState.Normal;
        }

        // 当收到第二个进程的通知时，显示窗体
        void OnProgramStarted(object state, bool timeout)
        {
            this.notifyIcon1.ShowBalloonTip(2000, "Hello", "I am here...", ToolTipIcon.Info);
            this.Show();
            this.WindowState = FormWindowState.Normal; //注意：一定要在窗体显示后，再对属性进行设置
        }
    }
}

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