linq初入交叉連接查詢，兩個對象之間分別匹配

類型 查詢變量= from 臨時變量 in 集合對象或數據庫對象

            [where 條件表達式]
            [order by 條件]
            select 臨時變量中被查詢的值
            [group by 條件]

            linq的分類：linq to objects,linq to datasets,linq to sql,linq to entities,linq to XML

下面是代碼練習：

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

namespace _71_linq交叉連接
{
    class Program
    {
        static void Main(string[] args)
        {
            //聲明兩個CHAR類型的數據源
            char[] upperCase = { 'A', 'B', 'C' };
            char[] lowerCase = { 'x', 'y', 'z' };

            var joinQuery1 =
                from upper in upperCase 
                from lower in lowerCase
                select new { upper, lower };

            var joinQuery2 =
                from lower in lowerCase
                from upper in upperCase
                select new { upper, lower };

            foreach (var pair in joinQuery1)
            {
                Console.WriteLine(string.Format("{0}匹配{1}", pair.upper, pair.lower));
            }

            foreach (var pair in joinQuery2)
            {
                Console.WriteLine(string.Format("{0}匹配{1}", pair.lower, pair.upper));
            }

            Console.ReadKey();

        }
    }
}