/// <summary>
        /// Distinct去除重複項（可自己指定）
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TKey"></typeparam>
        /// <param name="source"></param>
        /// <param name="keySelector"></param>
        ///
 
 <returns></returns>
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
        {
            HashSet<TKey> seenKeys = new HashSet<TKey>();
            foreach (TSource element in
 
 source)
            {
                if (seenKeys.Add(keySelector(element)))
                    yield return element;
            }
        }

使用方法如下（針對ID，和Name進行Distinct）

var query = people.DistinctBy(p => new { p.Id, p.Name });

若僅僅針對ID進行distinct：

var query = people.DistinctBy(p => p.Id);