C# List去重的比较器

public class user_collection_DistinctBy_userId : IEqualityComparer<User>    {

        public bool Equals(User x, User y)        {            if (x.UserId == y.UserId)            {                return true;            }            else            {                return false;            }        }

        public int GetHashCode(User obj)        {            return 0;        }    }