I forgot to include the code of the ListHelp object and method that's in the ItemDataBound event.
publicstaticvoidFillEmployees(RadComboBox list, int? selectedId = null){ var client = newUserServiceClient(); var userList = client.GetSecurityUsers(); list.ClearSelection(); list.Items.Clear(); list.Items.Add(newRadComboBoxItem("(Choose Employee)", "-1")); list.AppendDataBoundItems = true; list.DataSource = userList; list.DataValueField = "user_id"; list.DataTextField = "full_name_last_first"; list.DataBind(); if(selectedId.HasValue && selectedId.Value > 0) { if(list.FindItemByValue(selectedId.Value.ToString()) != null) { list.FindItemByValue(selectedId.Value.ToString()).Selected = true; } }}