如何与Nhibernate做一个条件和？

Question

我试图做到这一点SQL代码

SELECT 
ID 
SUM(CASE WHEN myProperty = 2 THEN 1 ELSE 0 END) as nbRowWithValueOf2, 
SUM(CASE WHEN myProperty = 3 THEN 1 ELSE 0 END) as nbRowWithValueOf3 
FROM Foo 
GROUP BY ID 

与NHibernate的等价物。

到目前为止，我试过

queryable = queryable 
    .Select(
     Projections.Group<Foo>(c => c.ID), 
     Projections.Sum<Foo>(c => c.myProperty == MyEnum.Two ? 1 : 0) 
     Projections.Sum<Foo>(c => c.myProperty == MyEnum.Three ? 1 : 0) 
) 

但是这给了我以下错误：

Could not determine member from IIF((Convert(c.myProperty) = 2), 1, 0)

你有什么想法？

编辑1：我可以得到2查询的结果，但我只想在1查询中做到这一点。

编辑2：我在这里使用QueryOver。

Answer 1

我认为这应该工作（QueryOver语法）：

queryover = queryover 
    .Select(
     Projections.Group<Foo>(c => c.ID), 
     Projections.Sum(
      Projections.Conditional(
       Restrictions.Where<Foo>(f => f.myProperty == MyEnum.Two), 
       Projections.Constant(1), 
       Projections.Constant(0))), 
     Projections.Sum(
      Projections.Conditional(
       Restrictions.Where<Foo>(f => f.myProperty == MyEnum.Three), 
       Projections.Constant(1), 
       Projections.Constant(0)))); 

这应该给你的SQL语句：

SELECT this_.ID as y0_, 
     sum((case 
       when this_.myProperty = 2 /* @p0 */ then 1 /* @p1 */ 
       else 0 /* @p2 */ 
      end))    as y1_, 
     sum((case 
       when this_.myProperty = 3 /* @p3 */ then 1 /* @p4 */ 
       else 0 /* @p5 */ 
      end))    as y2_ 
FROM [Foo] this_ 
GROUP BY this_.ID