You can use Timer Control by using ajax controls
<asp:timer id="Timer1" runat="server" interval="1000" ontick="Timer1_Tick" xmlns:asp="#unknown"></asp:timer>
<asp:lable id="Lable1" runat="server" xmlns:asp="#unknown" />
Add ontick event code in cs file:
protected void Timer1_Tick(object sender, EventArgs e)
{
int seconds;
if (Convert.ToString(Label1.Text) != "")
{
seconds = int.Parse(Label1.Text);
}
else
{
seconds =Convert.ToInt32(defaultTimer);
}
Session[timeout"] = (seconds - 1).ToString();
if (seconds> 0)
{
Label1.Text = (seconds - 1).ToString();
}
else
{
Timer1.Enabled = false;
}
}