linq学习笔记(一)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace LinqDemo

{
    class Program

    {

        static int[] numbers = { 1, 3, 4, 5, 6, 7, 8, 9, 10, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 };

        static void Main(string[] args)

        {

            Traditonal();

            Console.WriteLine("----------------------");

            LinqMethod();

            Console.ReadLine();

        }


        /// <summary>

        /// 传统写法

        /// </summary>

        static void Traditonal() 

        {
           
            List<int> SelectedNumbers = new List<int>();

            foreach (int i in numbers)

            {

                if (i % 2==0)

                {

                    SelectedNumbers.Add(i);                    

                }               

            }           

           
            SelectedNumbers.Sort(SortDesc); //.net1.0写法           

            for (int i = 0; i < SelectedNumbers.Count; i++)

            {

                Console.WriteLine(SelectedNumbers[i]);

            }
           
        }

        /// <summary>

        /// 逆顺排序(配合传统写法)

        /// </summary>

        /// <param name="x"></param>

        /// <param name="y"></param>

        /// <returns>1(x大于y),0(x等于y),-1(x小于y)</returns>

        static int SortDesc(int x,int y) 

        {

            //if (x < y) 

            //{

            //    return 1;

            //}

            //else if (x == y)

            //{

            //    return 0;

            //}

            //else 

            //{

            //    return -1;

            //}//也可以简写为下面的一行

            return y - x;

        }

        /// <summary>

        /// Linq的写法

        /// </summary>

        static void LinqMethod() 

        {
          
            var SelectedNumbers = from number in numbers where (number % 2 == 0) orderby number descending select number;

            foreach (var i in SelectedNumbers)

            {

                Console.WriteLine(i);

            }           

        }
       
    }

}