.NET(C#) LINQ Concat和Union的使用

1、Concat操作符

Concat操作符用于连接两个序列，生成一个新序列。

例如，

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            List<People> pList = new List<People>();
            People p1 = new People(1, "C", 4);
            People p2 = new People(2, "Java", 7);
            People p3 = new People(3, "Python", 11);
            People p4 = new People(4, "Linux", 15);
            pList.Add(p1);
            pList.Add(p2);
            pList.Add(p3);
            pList.Add(p4);
            List<People> pList1 = new List<People>();
            People p5 = new People(5,"CJavaPY",16);
            pList1.Add(p5);
            IEnumerable<People> newList = pList.Concat(pList1);
            foreach (var item in newList)
            {
                Console.WriteLine(item.Name);              
            }
            Console.ReadKey();
        }
    }
    public class People
    {
        public People(int id, string name, int age)
        {
            this.Id = id;
            this.Name = name;
            this.Age = age;
        }
        public int Id
        {
            get;
            set;
        }
        public string Name
        {
            get;
            set;
        }
        public int Age
        {
            get;
            set;
        }
    }
}

2、Union操作符

Union操作符用于将两个序列中的元素合并成一个新的序列，新序列将自动去除重复的元素。

例如，

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> listInt = new List<int>();
            listInt.Add(1);
            listInt.Add(2);
            listInt.Add(3);
            List<int> listInt1 = new List<int>();
            listInt1.Add(2);
            listInt1.Add(3);
            listInt1.Add(4);
             //Concat的使用
            IEnumerable<int> IEInt = listInt.Concat(listInt1);
            foreach (var i in IEInt)
            {
                Console.WriteLine(i);   
            }
            Console.WriteLine();
            //Union的使用
            IEnumerable<int> IEInt1 = listInt.Union(listInt1);
            foreach (var i in IEInt1)
            {
                Console.WriteLine(i);   
            }
             //根据输出结果可以看出Concat和Union的区别
            Console.ReadKey();
        }
    }
}