Linq-Enumerable类

摘自：C#高级功能（二）LINQ 和Enumerable类

		//group 分组
        var queryGroups =
            from score in scores
            group score by score;

        //into 存储查询的内容
         percentileQuery is an IEnumerable<IGrouping<int, Country>>
        var percentileQuery =
            from score in scores
            group score by score into scorequery
            where scorequery.Key > 10
            select scorequery;

        //在 from 开始子句以及 select 或 group 结束子句之间，
        //所有其他子句（where、join、orderby、from、let）都是可选的。 
        //任何可选子句都可以在查询正文中使用零次或多次。

        //let 子句
        //使用 let 子句可以将表达式（如方法调用）的结果存储到新的范围变量中。
        string[] names = { "a n", "b c", "c n", "d m" };
        IEnumerable<string> queryFirstNames =
            from name in names
            let firstName = name.Split(new char[] { ' ' })[0]
            select firstName;

        //对一个序列应用累加器函数。
        //Aggregate<TSource>(IEnumerable<TSource>, Func<TSource, TSource, TSource>)
        string sentence = "the quick brown fox jumps over the lazy dog";
        string[] words = sentence.Split(' ');
        string reversed = words.Aggregate((wording, next) => wording + " " + next);
        Console.WriteLine(reversed);