C# EF去除重复列DistinctBy

1.添加一个扩展方法

public static class DistinctByClass
    {
        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;
                }
            }
        }
    }　

2.使用方法如下（针对ID，和Name进行Distinct）

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

3.若仅仅针对ID进行distinct：

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