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

queryover = queryover

    .Select(

        Projections.Group<Foo>(c => c.ID),

        Projections.Sum(

            Projections.Conditional(

                Restrictions.Where<Foo>(f => f.myProperty == MyEnum.Two),

                Projections.Constant(),

                Projections.Constant())),

        Projections.Sum(

            Projections.Conditional(

                Restrictions.Where<Foo>(f => f.myProperty == MyEnum.Three),

                Projections.Constant(),

                Projections.Constant())));

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