Himall商城LinqHelper帮助类（1）

 ///

        /// 去重复项
        ///

        ///
        ///
        ///
        ///
        ///
        public static IEnumerable DistinctBy(this IEnumerable source, Func keySelector)
        {
            HashSet seenKeys = new HashSet();
            foreach (TSource element in source)
            {
                if (seenKeys.Add(keySelector(element)))
                {
                    yield return element;
                }
            }
        }