How to store the Logout time in database when user closes tab or Browser in Asp.Net

i want to kill the session on the browser closing or tab closing and store the Logout time in database using Asp.Net.

i have coded that code in Global.asax page which works only when we Click on Logout Button .but it's not worked on the tab closing /Browser closing. Pleas Help !!!!

void Session_End(object sender, EventArgs e) 
    { 


SqlTransaction transection = null;
            using (SqlConnection con = new SqlConnection(conn))
            {
                con.Open();
                SqlCommand cmd = con.CreateCommand();
                transection = con.BeginTransaction("Transactions");
                cmd.Connection = con;
                cmd.Transaction = transection;
                cmd.Parameters.Clear();
                
             
                    {
                        cmd.Parameters.Clear();
                        cmd.CommandText = "UPdate Login_Prevention Set logout_time=@logout,offline='1' where offline='0' AND SID=@sid AND username=@username";
                        cmd.Parameters.AddWithValue("@logout",date1);
                        cmd.Parameters.AddWithValue("@sid",online_user[i].ToString());

cmd.Parameters.AddWithValue("@username",session["member"].Tostring());

cmd.ExecuteNonQuery(); } transection.Commit(); } } }