using System.Collections.Generic;

namespace System
{
    //From https://github.com/Burtsev-Alexey/net-object-deep-copy
    public static class ObjectExtensions
    {
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
        {
            var seenKeys = new HashSet<TKey>();
            foreach (var element in source)
            {
                if (seenKeys.Add(keySelector(element)))
                {
                    yield return element;
                }
            }
        }

    }
}