namespace ServiceCenter.Extensions
{
    /// <summary>
    /// Linq 扩展
    /// </summary>
    public static class LinqExtension
    {
        /// <summary>
        /// 根据指定的属性返回集合中的非重复元素
        /// </summary>
        /// <typeparam name="TSource">数据源的类型</typeparam>
        /// <typeparam name="TKey">数据源需要进行筛选的属性</typeparam>
        /// <param name="source">数据源</param>
        /// <param name="keySelector">指定属性的函数表达式</param>
        /// <returns></returns>
        public static IEnumerable<TSource> DistinctItemBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
        {
            var seenKeys = new HashSet<TKey>();
            foreach (var source1 in source)
            {
                if (seenKeys.Add(keySelector(source1)))
                    yield return source1;
            }
        }
    }
}