LinQ基本使用：查询数组

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/*
            Linq: Language INtegrated Query语言级集成查询
            LinQ通常在数组，泛型集合，IEnumerable等
            关键字：from ，in , where , orderby, select new {v1=stra,v1=strb}
            from:  变量或对象 多个数据源 嵌套语句
            in:查询的数据源
            where: 条件 可允许多个where字句,但表示的是并列关系,表达式最好用（）括起来
            orderby: 指定排序字段，可以是升序或降序，多个间逗号分隔
            select:指定返回目标内容
            group：对象 by 对象的属性或字段，分组
            join：连接多个数据源，后面必须跟 on 关键字
            LInq查询必须是以select子句或者group by子句结尾
            lanmda 表达式  "=>"
            */
            #endregion
            #region 查询数组

            Console.WriteLine("查询数组\r\n");
            int[] arr = new int[] { 12, 34, 45, 3, 11, 18 };
            int[] arr2 = new int[] { 25, 58, 34, 94, 43, 38, 48, 9 };

            //匿名对象, 查询变量
            var m_1 = from m in arr
                      select m;
            
            //where子句
            var m0 = from m in arr
                     where m % 2 == 0
                     select m;
            //多个where子句是并列关系
            var m2 = from m in arr
                     where m >= 10
                     where m <= 20
                     where m % 2 == 0
                     select m;

            //也可以这样写
            var m3 = from m in arr
                     where (m >= 10) && (m <= 20) && (m % 2 == 0)
                     select m;

            //orderby排序，ascending-升序;descending-降序 多个排序条件使用逗号分隔
            var m1 = from n in arr
                     where n % 2 == 1
                     orderby n ascending
                     select n;

            //多数据源
            var m4 = from m in arr
                     from n in arr2
                     where m == n
                     select new { var1 = m, var2 = n };

            //select子句后面可以跟 匿名对象
            //可以给匿名对象的成员取别名
            foreach (var item in m4)
            {
                Console.WriteLine(item);
            }