private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
  //MessageBox.Show("程序将最小化到系统托盘区");
  e.Cancel = true; // 取消关闭窗体
  this.Hide();
  this.ShowInTaskbar = false;//取消窗体在任务栏的显示
  this.notifyIcon1.Visible = true;//显示托盘图标
}

private void menuShow_Click(object sender, EventArgs e)
{
  this.Show();
  this.ShowInTaskbar = true;
  this.notifyIcon1.Visible = false;
}
private void menuExit_Click(object sender, EventArgs e)
{
  this.Dispose(true);
  Application.ExitThread();
}

private void notifyIcon1_MouseClick(object sender, MouseEventArgs e)
{
  if (e.Button == MouseButtons.Left)
  {
    this.Show();
    this.ShowInTaskbar = true;
    this.notifyIcon1.Visible = false;
  }
}

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Threading;
namespace LuceneTest
{
  static class Program
  {
    /// <summary>
    /// 应用程序的主入口点。
    /// </summary>
    [STAThread]
    static void Main()
    {
      bool bCreatedNew;
      Mutex m = new Mutex(false, "Product_Index_Cntvs", out bCreatedNew);
      if (bCreatedNew)
      {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
      }
    }
  }
}