Creating a system tray app with menu

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C#

C#4.0

I want a menu while I am clicking the icon in system tray.

My code is:

public ContextMenu traymenu;

public Form()
       {
           InitializeComponent();
           this.Resize += new EventHandler(Login_Resize);
       }
private void Form_Load(object sender, EventArgs e)
       {
           this.WindowState = FormWindowState.Minimized;
           this.Visible = false;
       }
private void Login_Resize(object sender, EventArgs e)
        {
            if (this.WindowState == FormWindowState.Minimized)
            {
                this.ShowIcon = false;
                this.ShowInTaskbar = false;
                notifyIcon1.Visible = true;
                notifyIcon1.BalloonTipTitle = "Minimized to Start Menu Bar";
                notifyIcon1.BalloonTipText = " Chat App minimized"; 
                notifyIcon1.ShowBalloonTip(15);

                traymenu = new ContextMenu();
                traymenu.MenuItems.Add("Logout", OnExit);
                this.Hide();
            }
            else if (FormWindowState.Normal == this.WindowState)
            {
                notifyIcon1.Visible = false;
            }
        }
private void OnExit(object sender, EventArgs e)
       {
           System.Environment.Exit(0);
       }
private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e)
       {
         traymanu.Show();  // showing error in this line
       }

solution need:
I need the contextmenu to be displayed while I am clicking the notify icon