ActiveRecord group by query

One day , I need use "group by " query,
but i don't know how to write it on ActiveRecord,

I try mony method, but i can't get the results. i am also post a thread to forum of caslte, but no one replay it ,may be it is so easy.
so ,  i redo my work. i found ,
i can use

            "select table.name,count(table.name) from Table table group by table.name order by table count(table.name) desc"

My gold, Is correct now.

HqlBasedQuery query = new HqlBasedQuery(typeof(ActivityInfo), hql);
            return ExecuteQuery(query);

How to get the data? like below

 ArrayList list = o as ArrayList;
        for(int i=0;i<list.Count;i++)
        }

and I found in activeRecord you can use SQL language to query, just set QueryLanguage to sql,

anthor method: Navtie Query