急！！！！！在线等！C# List！！！！！！！！！！！！！！！！！

[zdw_asp]

现有个User 对象，里面有 IDa，IDb，IDc，IDd，name；通过IDa，IDb，IDc，IDd，四个ID，判断是同一个user；
List<User> list = new List<User>();
User user = new User（）；
list里面有N条数据,过滤重复的user，就是说把list里面 IDa，IDb，IDc，IDd，相同的 user过滤掉，只保留一个；使list中没有重复的user

[guoyanhong1111]

1.在循环外定义一个list.
2.遍历个循环，判断user对象是否相同，如果不同则放入一个定义好的list中，如果相同这不添加到list

[枪牌]

方法1：在每一个list.Add前判断list中是否已存在user，如果存在，则不Add
方法2：重载list的Add方法，在Add方法中判断list中是否已存在user，如果存在，则不Add
方法3：为User实现ICompare接口，这样在方法2中的代码看起来就好多了

[zdw_asp]

  User user1 = new User() { IIDa = 1, IIDb = 1, IIDc = 1, IIDd = 1, Name = "a", Value = 3 };
            User user2 = new User() { IIDa = 2, IIDb = 2, IIDc = 2, IIDd = 2, Name = "b", Value = 3 };
            User user3 = new User() { IIDa = 1, IIDb = 1, IIDc = 1, IIDd = 1, Name = "a", Value = 3 };
            User user4 = new User() { IIDa = 1, IIDb = 1, IIDc = 1, IIDd = 1, Name = "s", Value = 3 };
            User user5 = new User() { IIDa = 2, IIDb = 2, IIDc = 2, IIDd = 2, Name = "d", Value = 3 };
            User user6 = new User() { IIDa = 3, IIDb = 3, IIDc = 3, IIDd = 3, Name = "c", Value = 3 };
            User user7 = new User() { IIDa = 3, IIDb = 3, IIDc = 3, IIDd = 3, Name = "e", Value = 3 };
            User user8 = new User() { IIDa = 3, IIDb = 3, IIDc = 3, IIDd = 3, Name = "f", Value = 3 };
            User user9 = new User() { IIDa = 3, IIDb = 3, IIDc = 3, IIDd = 3, Name = "g", Value = 3 };
            List<User> list = new List<User>();
            list.Add(user1);
            list.Add(user2);
            list.Add(user3);
            list.Add(user4);
            list.Add(user5);
            list.Add(user6);
            list.Add(user7);
            list.Add(user8);
            list.Add(user9);
            List<User> list1 = new List<User>();
            for (int i = 0; i < list.Count; i++)
            {
                if (list1.Count != 0)
                {
                    var n = from a in list1 where a.IIDa == list[i].IIDa && a.IIDb == list[i].IIDb && a.IIDc == list[i].IIDc && a.IIDd == list[i].IIDd select a;
                    if (n.ToList().Count == 0)
                    {
                        list1.Add(list[i]);
                    }
                }
                else
                {
                    list1.Add(list[i]);
                }
            }

这样逻辑有没有问题？

[bdmh]

[Quote=引用 3 楼 zdw_asp 的回复:]
C# code

User user1 = new User() { IIDa = 1, IIDb = 1, IIDc = 1, IIDd = 1, Name = "a", Value = 3 };
User user2 = new User() { IIDa = 2, IIDb = 2, IIDc = 2, IIDd = 2, Name = "b", Value……
[/Quote]
应该可以

[机器人]

用Linq就简单很多了：
方法1： group by
方法2： Distinct

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

namespace LinqDistinctTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var query1 = from a in GetData()
                        group a by new { a.A } into g
                        select g.FirstOrDefault();

            foreach (var u in query1)
                Console.WriteLine(u.ToString());

            Console.WriteLine("=============");

            var compare = new UserCompare();
            var query2 = GetData().Distinct(compare);

            foreach (var u in query2)
                Console.WriteLine(u.ToString());

            Console.WriteLine("=============");

            Console.Read();
        }

        static List<User> GetData()
        {
            return new List<User> { 
                new User { A = "a1", B = "b1", C = "c1", D = "d1" },
                new User { A = "a1", B = "b1", C = "c1", D = "d1" },
                new User { A = "a2", B = "b1", C = "c1", D = "d1" },
                new User { A = "a1", B = "b2", C = "c1", D = "d1" },
                new User { A = "a1", B = "b1", C = "c1", D = "d1" },
                new User { A = "a1", B = "b1", C = "c2", D = "d1" },
                new User { A = "a1", B = "b1", C = "c1", D = "d2" },
            };
        }
    }

    class UserCompare : IEqualityComparer<User>
    {
        #region IEqualityComparer<User> Members

        public bool Equals(User x, User y)
        {
            return (x.A == y.A && x.B == y.B && x.C == y.C && x.D == y.D);
        }

        public int GetHashCode(User obj)
        {
            return obj.ToString().ToLower().GetHashCode();
        }

        #endregion
    }

    class User
    {
        public string A;
        public string B;
        public string C;
        public string D;

        public override string ToString()
        {
            return string.Format("{0},{1},{2},{3}", A, B, C, D);
        }
    }
}

[claymore1114]

直接分组，取 每一组的一条

List<User> list = new List<User>();
var query = list.GroupBy(g => new { g.IDa,g.IDb,g.IDc,g.IDd }).Select(s=>s.FirstOrDefault());

[yalan]

我也赞同3楼，这样应该可以

[billsquall]

where a.IIDa == list[i].IIDa && a.IIDb == list[i].IIDb && a.IIDc == list[i].IIDc && a.IIDd == list[i].IIDd select a;

你这个是所有id都相同的取出来不要了？

或者你循环的时候把这些ID都串在一起，放hashtable里也不错啊，直接判断key

key=IDa+"，"+IDb+"，"+IDc+"，"+IDd
value=user