Change Icon Notify on Click

Further to the first answer, this sample[^] (though in VB.Net) should help you out.

Show progress using the NotifyIcon application tray icon[^] should help you out as well.

using System;
using System.Drawing;
using System.Windows.Forms;

public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.NotifyIcon notifyIcon1;
private System.Windows.Forms.ContextMenu contextMenu1;
private System.Windows.Forms.MenuItem menuItem1;
private System.ComponentModel.IContainer components;

[STAThread]
static void Main()
{
Application.Run(new Form1());
}

public Form1()
{
this.components = new System.ComponentModel.Container();
this.contextMenu1 = new System.Windows.Forms.ContextMenu();
this.menuItem1 = new System.Windows.Forms.MenuItem();

// Initialize contextMenu1
this.contextMenu1.MenuItems.AddRange(
new System.Windows.Forms.MenuItem[] {this.menuItem1});

// Initialize menuItem1
this.menuItem1.Index = 0;
this.menuItem1.Text = "E&xit";
this.menuItem1.Click += new System.EventHandler(this.menuItem1_Click);

// Set up how the form should be displayed.
this.ClientSize = new System.Drawing.Size(292, 266);
this.Text = "Notify Icon Example";

// Create the NotifyIcon.
this.notifyIcon1 = new System.Windows.Forms.NotifyIcon(this.components);

// The Icon property sets the icon that will appear
// in the systray for this application.
notifyIcon1.Icon = new Icon("appicon.ico");

// The ContextMenu property sets the menu that will
// appear when the systray icon is right clicked.
notifyIcon1.ContextMenu = this.contextMenu1;

// The Text property sets the text that will be displayed,
// in a tooltip, when the mouse hovers over the systray icon.
notifyIcon1.Text = "Form1 (NotifyIcon example)";
notifyIcon1.Visible = true;

// Handle the DoubleClick event to activate the form.
notifyIcon1.DoubleClick += new System.EventHandler(this.notifyIcon1_DoubleClick);

}

protected override void Dispose( bool disposing )
{
// Clean up any components being used.
if( disposing )
if (components != null)
components.Dispose();

base.Dispose( disposing );
}

private void notifyIcon1_DoubleClick(object Sender, EventArgs e)
{
// Show the form when the user double clicks on the notify icon.

// Set the WindowState to normal if the form is minimized.
if (this.WindowState == FormWindowState.Minimized)
this.WindowState = FormWindowState.Normal;

// Activate the form.
this.Activate();
}

private void menuItem1_Click(object Sender, EventArgs e) {
// Close the form, which closes the application.
this.Close();
}
}