Progress Bar In Asp .Net With Ajax

protected void Page_Load(object sender, EventArgs e)

{
if (!IsPostBack)
{
Label1.Text = DateTime.Now.ToLongTimeString();
Label2.Text = DateTime.Now.ToLongTimeString();
}
}

The Progress Bar Button Click then Progress bar is Working as You see Image

protected void ProgressBarButton_Click(object sender, EventArgs e)
{
System.Threading.Thread.Sleep(3000);
Label2.Text = DateTime.Now.ToLongTimeString();
}