最小化到托盘，右键退出

 private void toolStripMenuItem1_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }     

 if (this.WindowState == FormWindowState.Minimized)    //最小化到系统托盘
            {
                this.notifyIcon1.Visible = true;    //显示托盘图标
                this.Hide();    //隐藏窗口
            }

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            //注意判断关闭事件Reason来源于窗体按钮，否则用菜单退出时无法退出!
            if (e.CloseReason == CloseReason.UserClosing)
            {
                e.Cancel = true;    //取消"关闭窗口"事件
                this.WindowState = FormWindowState.Minimized;    //使关闭时窗口向右下角缩小的效果
                this.notifyIcon1.Visible = true;
                this.Hide();
                return;
            }
        }