过滤掉List<object>中重得的项

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


namespace ConsoleApplication5
{
    class Program
    {
       
        staticvoid Main(string[] args)
        {
            List<item> list =new List<item>();

            list.Add(new item { item1 =1, item2 ="b", item3 =4.0,item4=8 });  
            list.Add(new item { item1 =1, item2 ="a", item3 =1.0 ,item4=9});
            list.Add(new item { item1 =2, item2 ="a", item3 =1.0 ,item4=7});
            list.Add(new item { item1 =3, item2 ="a", item3 =1.0 ,item4=6});
            list.Add(new item { item1 =1, item2 ="a", item3 =2.0 ,item4=5});

            

            List<item> temp = list.Distinct(new item_collection_DistinctBy_item1()).ToList();

            foreach (var item in temp)
            {
                Console.WriteLine(item);
            }
            Console.Read();
        }
    }

    class item
    {
        publicint item1
        { get; set; }

        publicstring item2
        { get; set; }

        publicdouble item3
        { get; set; }

        publicint item4
        { get; set; }

        publicoverridestring ToString()
        {
            returnstring.Format("item1:{0},item2:{1},item3:{2},item4:{3}", item1, item2, item3,item4);
        }
    }

    class item_collection_DistinctBy_item1 : IEqualityComparer<item>
    {
        
        publicbool Equals(item x, item y)
        {
            if (x.item1 == y.item1 && x.item3 == y.item3)
            {
                returntrue;
            }
            else
            {
                returnfalse;
            }
        }

        publicint GetHashCode(item obj)
        {
            return0;
        }
    }
  
}