group by with repository and entity framework

i have this entity framework code:
 

repository.GetObjectQuery(Of COUNL1)().Where(Function(a) a.CDATE >= "2012/01/01" And a.CDATE <= "2012/12/01" And COID = 88 ).GroupBy(Function(m) m.CDATE).Select(Function(n) New PointXY With {.Y = n.Sum(Function(k) k.TOTALVH), .X = n.First().CDATE}).ToList

this error accoured:

Only parameterless constructors and initializers are supported in LINQ to Entities.

 
description:
i want group by CDATE and sum of TOTALVH and put it in PointXY Class Like this

PointXY {.Y = Sum(TOTALVH), .X = CDATE})

sql Query :

    SELECT        SUM(TOTALVH) AS EXPR1, CDATE
    FROM            COUNL1
    WHERE        (CDATE >= '2012/01/01') AND (CDATE <= '2012/12/01') AND   (COID  = 88)
    GROUP BY CDATE

 
please help me,thanks all.