Cross Apply in LinQ to Entities with Scalar Value

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C#

LINQ

Look at the following three tables. One: Trainee Info, two: Batch and three: Attendance.

Trainee join with batch by BatchId and then count attendance of trainee's from attendance table which required cross apply. Though I can finish it in the following way:

select 
	A.Id,
	A.TraineeName,
	B.BatchNo,
	AttendanceCount=(Select AttendanceCount=Count(*) from @TA2 A_A where A.Id=A_A.TraineeId)
from @TA1 A
inner join @TB1 B on A.BatchId=B.Id

But here I would like to use cross apply. Following sql code working well in Sql Server.

--Trainee Info
DECLARE @TA1 TABLE
(
  Id int,
  BatchId int,
  TraineeName varchar(50)
)
--Batch
DECLARE @TB1 TABLE
(
  Id int,
  BatchNo varchar(50)
)

--Attendance
DECLARE @TA2 TABLE
(
  Id int,
  TraineeId varchar(50),
  AttendanceDate datetime
)
--batch
insert into @TB1 values(1,'C#-B1')
insert into @TB1 values(2,'J2EE-B1')
insert into @TB1 values(3,'Networking-B1')

--Trainee
insert into @TA1 values(1,1,'AAA')
insert into @TA1 values(2,1,'ABC')
insert into @TA1 values(3,2,'ADC')
insert into @TA1 values(4,3,'AEB')

--Attendance Date
insert into @TA2 values(1,1,getdate())
insert into @TA2 values(1,2,getdate())
insert into @TA2 values(1,1,getdate())
insert into @TA2 values(1,2,getdate())
insert into @TA2 values(1,3,getdate())

select 
	A.Id,
	A.TraineeName,
	B.BatchNo,
	C.AttendanceCount 
from @TA1 A
inner join @TB1 B on A.BatchId=B.Id
cross apply (Select AttendanceCount=Count(*) from @TA2 A_A where A.Id=A_A.TraineeId) C

Come to linq to entitiy where cross apply is working fine while table doesn't return scalar value.

var query = from a1 in context.TA1
			join b1 in context.TB1 on a1.BatchId equals b1.Id
            from a2 in context.TA2
            Where(a2.TraineeId == a.Id)
            select new
            {
				a1.Id,
				a1.TraineeName,
				b1.BatchNo,
				a2.AttendanceDate 
            };

but if I want to Count instead of a2.AttendanceDate what shall I do?

var query = from a1 in context.TA1
			join b1 in context.TB1 on a1.BatchId equals b1.Id
            from a2 in context.TA2
                             .Where(x => x.TraineeId == a.Id).Count() //getting Errror ????
            select new
            {
				a1.Id,
				a1.TraineeName,
				b1.BatchNo,
				a2.AttendanceDate //?????????
            };

Thanks
Asif