To minimize windows form to the system tray, follow these steps.

1. Create your new C# project.
2. From the toolbox, drag the NotifyIcon to your form.
3. On your Form_Load event, copy and paste the following code:

private void Form1_Load(object sender, EventArgs e)  
{  
notifyIcon1.BalloonTipText = "This application was minimized to tray";  
notifyIcon1.BalloonTipTitle = "My Sample Application";  
   
//Display the Notify Baloon for 1 second  
notifyIcon1.ShowBalloonTip(1000);  
   
//Set the WindowState in Minimized Mode  
WindowState = FormWindowState.Minimized;  
}  


 Then on Form_Resize event, add this code.
    private void Form1_Resize(object sender, EventArgs e)  
    {  
//On minimize mode, show the form in System Tray only  
        if (FormWindowState.Minimized == WindowState)  
        {  
            Hide();  
        }  
    }  


Now to restore the form upon double-click on NotifyIcon control.
    private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e)  
    {  
//Display the Form in normal state  
        WindowState = FormWindowState.Normal;  
        Show();  
    }