扩展IEnumerable排重方法

    /// <summary>
    /// 扩展IEnumerable排重方法
    /// </summary>
    public static class IEnumerable
    {
        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（针对ID，和Name进行Distinct）
var query = people.DistinctBy(p => new { p.Id, p.Name });

若仅仅针对ID进行distinct：
var query = people.DistinctBy(p => p.Id);