Linq分组操作之GroupBy,GroupJoin扩展方法源码分析

 var query = from n in list
                        group n by n
                      into grp
                        select new
                        {
                            MyKey = grp.Key,
                            MyValue = grp.Count()
                        };

  //如下： 会以Key 为分组，与sql一样
            var wordList = new List<word>()
            {
                new word { Key="dragon", length=1, str=""},
                new word { Key="dragon", length=21, str=""},
                new word { Key="joc", length=31, str=""}

            };
            var keyCount = wordList.GroupBy(i=>i.Key).ToArray();

        var query2 = from n in wordList
                         join m in word2List
                         on n.Key equals m.Key
                         into grp
                         select new
                         {
                             Key = n.Key,
                             Value = grp.Count()
                         };