nhibernate:帮助将HQL查询转换为使用条件API

我有下面的HQL查询,我想切换到标准API

select a.Id as Id, a.Name as Name, a.ActiveStatus as ActiveStatus, 
dbo.GetActivityStartDate(a.Id) as StartDate, 
dbo.GetActivityEndDate(a.Id) as EndDate, 
coalesce(ac.Id,0) As CategoryId, 
coalesce(ac.Name,'') As CategoryName 
from Activity as a 
left outer join a.Category as ac 

显然,选择行上的初始属性是微不足道的(projects.property);我的问题是..如何映射剩余的4个属性?

我有一种习惯的方言 dbo.GetActivityStartDate 和 dbo.GetActivityEndDate 作为标准的SQL函数-所以已经考虑了很多。