Display Session Expired (Timeout) message in ASP.Net

Check this example it works fine for me in Visual Studio.

HTML

<form id="form1" runat="server">
<asp:Button ID="btnReset" Text="Reset" runat="server" OnClick="ResetSession" />
<br />
Your Session will expire in <span id = "seconds"></span> seconds.
<script type="text/javascript">
    function SessionExpireAlert(timeout) {
        var seconds = timeout / 1000;
        seconds--;
        document.getElementById("seconds").innerHTML = seconds;
        setInterval(function () {
            seconds--;
            document.getElementById("seconds").innerHTML = seconds;
        }, 1000);
        setTimeout(function () {
            alert("Your session has expired. You will now be redirected.");
            window.location = "Expired.aspx";
        }, timeout);
    }
</script>
</form>

Namespaces

using System.Configuration;
using System.Web.Configuration;

Code

protected void Page_Load(object sender, EventArgs e)
{
    Session["Name"] = "Mudassar";
    Configuration config = WebConfigurationManager.OpenWebConfiguration("~/Web.Config");
    SessionStateSection section = (SessionStateSection)config.GetSection("system.web/sessionState");
    int timeout = (int)section.Timeout.TotalMinutes * 1000 * 60;
    ClientScript.RegisterStartupScript(this.GetType(), "SessionAlert", "SessionExpireAlert(" + timeout + ");", true);

}

protected void ResetSession(object sender, EventArgs e)
{
    string name = Session["Name"].ToString();
}

Web.Config

<sessionState timeout="1"/>