How to redirect to the login page automatically when session timeout in asp.net C#

Here i am showing how to redirect to the login page automatically when session timeout in asp.net C#

Write this code in to the masterpage's cs file

protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
this.HeadContent.Controls.Add(new LiteralControl(
String.Format("<meta http-equiv='refresh' content='{0};url={1}'>",
SessionTimeOutWithin * 60, PageToSentAfterSessionTimeOut)));
}
This will add a metatag into the page header which will refresh the CheckSessionTimeOut.aspx page after SessionTimeOutWithin* 60 seconds when the session timeout occurs.

//This the page to be refresh after sessioin timeout
public string PageToSentAfterSessionTimeOut
{
get { return "CheckSessionTimeOut.aspx"; }
}

//This takes the Session.Timeout from the webconfig or from where the Session.Timeout is being set
public int SessionTimeOutWithin
{
get { return Session.Timeout; }
}

// Add this within the <system.web> tag in web.config file . Here i am set 1 min as Session timeout

<sessionState mode="InProc" cookieless="true" timeout="1"></sessionState>

This will set the session timeout as 1 minute

Mode: means what happens if page is in active mode , InProc means session timeout will increase 1 minute more after the page activity time but if the page is in idle for 1 minute then session timeout will occurs.