public void bind_city() { try { bl.Category = ddl_state.SelectedValue; dtt = dl.bind_city(bl); ddl_city.Items.Clear(); ddl_city.DataSource = dtt.table; ddl_city.DataTextField = "Name"; ddl_city.DataValueField = "Id"; ddl_city.DataBind(); ddl_city.Items.Insert(0, new ListItem("Select City", "0")); } catch (NullReferenceException) { // Utilities.MessageBox_UpdatePanel_Redirect(UpdatePanel2, "Your Session Has Expired Please Login Again", "../Logout.aspx"); } }