SELECT IDSUM(CASE WHEN myProperty = 2 THEN 1 ELSE 0 END) as nbRowWithValueOf2,SUM(CASE WHEN myProperty = 3 THEN 1 ELSE 0 END) as nbRowWithValueOf3FROM FooGROUP BY ID

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

生成SQL

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