在窗体上放个 notifyIcon1 和contextMenuStrip1，将notifyIcon1的contextMenuStrip设为contextMenuStrip1
在contextMenuStrip1上加入open 和 exit 项

        private void ToolStripMenuItemOpen_Click(object sender, EventArgs e) {
            this.ShowInTaskbar = true;
            this.WindowState = FormWindowState.Normal;
            this.TopMost = true;        //这里如果用this.bringToFront()可以
            this.TopMost = false;
        }
       
        private void notifyIcon1_DoubleClick(object sender, EventArgs e) {
            this.ShowInTaskbar = true;
            this.WindowState = FormWindowState.Normal;
            this.TopMost = true;          //这里如果用this.bringToFront()则无效，搞不懂
            this.TopMost = false;
        }

        private void MainForm_FormClosing(object sender, FormClosingEventArgs e) {
            this.WindowState = FormWindowState.Minimized;      //这句必须放在第二句前面，否则会在左下角有个小标题栏
            this.ShowInTaskbar = false;
            e.Cancel = true;
        }
       
        private void ToolStripMenuItemExit_Click(object sender, EventArgs e) {
            Application.ExitThread();
        }

//-------------------------------------------------------------------------------------------------------------------------
修改如下：
        private void openToolStripMenuItem_Click(object sender, EventArgs e) {
            this.Visible = true;
            this.WindowState = FormWindowState.Normal;
        }

        private void exitToolStripMenuItem_Click(object sender, EventArgs e) {
            Application.ExitThread();
        }

        private void notifyIcon1_DoubleClick(object sender, EventArgs e) {
            this.Visible = true;
            this.WindowState = FormWindowState.Normal;
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
            e.Cancel = true;
            this.Visible = false;
        }