Получение списка содержащего только уникальные значения

public static DataTable GetDestinctValuesFromSPListItemCollection(SPListItemCollection collection, string getUniqueValuesFromFieldName, string sortByFieldName)
        {
            if (collection == null || string.IsNullOrEmpty(getUniqueValuesFromFieldName) || string.IsNullOrEmpty(sortByFieldName))
                return null;

            if (collection.Count > 0)
            {
                SPList list = collection[0].ParentList;
                DataTable dTable = collection.GetDataTable();
                DataView dataView = new DataView(dTable);
                dataView.Sort = list.Fields[sortByFieldName].InternalName; //for sort
                dTable = dataView.ToTable(true, list.Fields[getUniqueValuesFromFieldName].InternalName);
                dataView.Dispose();
                return dTable;
            }
            else
                return null;
        }