Call Server Side Method on Browser Window Close Button in ASP.Net

As I told you you need to make use of Session_End event of the Global.asax file.

You will have to store SessionId in the table and then delete using the SessionId

//To get SessionId
Session["Session"] = "session";
string s = Session.SessionID;

//To delete using SessionId in Global.asax
 void Session_End(object sender, EventArgs e)
        {
            DeleteUserEntry(Session.SessionID);
        }