List操作

http://blog.csdn.net/qq_23846795/article/details/77092670

http://blog.csdn.net/qq_23846795/article/details/78392758

List 去重

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

namespace NonDuplicateList
{
    class Program
    {
        static void Main(string[] args)
        {
            List<User> users = new List<User>();
            users.Add(new User("张三", "永丰路299号"));
            users.Add(new User("张三", "上地西路8号"));//重复项，去重后将删掉
            users.Add(new User("李四", "海鹰路甲一号"));

            List<User> nonDuplicateList1 = users.Distinct().ToList();//通过User类的Equals实现去重
            List<User> nonDuplicateList2 = users.Where((x,i)=>users.FindIndex(z=>z.name == x.name) == i).ToList();//Lambda表达式去重
            List<User> nonDuplicateList3 = new List<User>();//通过循环方式去重
            foreach(User user in users)
            {
                if(nonDuplicateList3.Exists(x=>x.name==user.name) == false)
                {
                    nonDuplicateList3.Add(user);
                }
            }

            foreach(List<User> list in new Object[]{nonDuplicateList1,nonDuplicateList2,nonDuplicateList3})//打印出三个List的元素
            {
                Console.Write("nonDuplicateList:
");
                foreach(User u in list)
                {
                    Console.WriteLine("	" + u.ToString());
                }
            }
            Console.Read();
        }
    }

    class User:IEquatable<User>//继承IEquatable接口，实现Equals方法。List就可以使用Distinct去重
    {
        public string name { get; set; }
        string address;

        public User(string _name, string _address)
        {
            name = _name;
            address = _address;
        }

        public override string ToString()
        {
            return string.Format("name:{0},	address:{1}", name, address);
        }

        public bool Equals(User other)
        {
            return this.name == other.name;
        }
        public override int GetHashCode()
        {
            return name.GetHashCode();
        }
    }
}

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

namespace ConsoleApplication11
{
    class MapCross : IEquatable<MapCross>//继承IEquatable接口，实现Equals方法。List就可以使用Distinct去重  
    {
        public int Id { get; set; }

        public string Name { get; set; }

        public override string ToString()
        {
            return "ID: " + Id + "   Name: " + Name;
        }
        public bool Equals(MapCross other)
        {
            return this.Name == other.Name;
        }
        public override int GetHashCode()
        {
            return Name.GetHashCode();
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            List<MapCross> list = new List<MapCross>();
            //添加
            list.Add(new MapCross { Id = 1, Name = "A" });
            list.Add(new MapCross { Id = 2, Name = "B" });
            list.Add(new MapCross { Id = 2, Name = "B" });
            list.Add(new MapCross { Id = 3, Name = "C" });
            list.Add(new MapCross { Id = 3, Name = "C" });
            list.Add(new MapCross { Id = 4, Name = "D" });
            //分组
            var query1 = from l in list
                        group l by new { l.Id, l.Name } into g
                        select new
                        {
                            Id = g.Select(o => o.Id).Sum(),
                            Name = g.Key.Name,
                            Count = g.Count(),
                        };
            //赋值
            foreach (var item in query1)
            {
                    MapCross cross = new MapCross();
                    cross.Id = item.Id;
                    cross.Name = item.Name;
                    list.Add(cross);
            }
            // 查询 赋值
            var newlist = (from a in list
                          where a.Name == "C"
                          select a).ToList();
            foreach (var item in newlist)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine();
            //相加
            list.AddRange(newlist);
            Console.WriteLine("相加");
            foreach (var item in list)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("剔除重复项");
            var list1= list.Union(list).ToList();          //剔除重复项 
            foreach (var item in list1)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("保留重复项");
            var list2 = list.Concat(newlist).ToList();        //保留重复项
            foreach (var item in list2)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("自身去重复 方法一");
            var list3=list.Distinct().ToList();
            foreach (var item in list3)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("自身去重复 方法二");
            //Lambda表达式去重  
            var list4 = list.Where((x, i) => list.FindIndex(z => z.Name == x.Name) == i).ToList();
            foreach (var item in list4)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("自身去重复 方法三");
            var list5 = new List<MapCross>();//通过循环方式去重  
            foreach (var u in list)
            {
                if (list5.Exists(x => x.Name == u.Name) == false)
                {
                    list5.Add(u);
                }
            }
            foreach (var item in list5)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("修改");
            //修改
            foreach (var item in list)
            {
                if (item.Name == "B")
                    item.Name = "BB";
            }
            //倒序for 才能删除
            for (int i = list.Count - 1; i >= 0; i--)
            {
                if (list[i].Name == "C")
                    list.Remove(list[i]);
            }
            //排序
            foreach (var item in list.OrderBy(s=>s.Name))
            {
                Console.WriteLine(item);
            }
           //复制
            //相减
            //关联

            Console.Read();
        }
    }
}