linq group by month problem

I want to count activity in a given month. I'm trying to do so with
the linq code below however it reports:
Error * 1 * * * 'a' is inaccessible due to its protection level
>
* * * * * * * * var ActivityByMonths = from a in db.ActivityDatas
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *where a.BeginDateTime >= From && a.BeginDateTime <= To
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *where a.SubActivityId ==sat
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *group a by a.BeginDateTime.Month into mg
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *select new { a.BeginDateTime..Month, count = mg.Count() };
>
I want to select is the month number and the number of activities that
took place in that month.

On Jul 17, 5:39*pm, Seb <sebastianthegreat...@gmail.comwrote:
>>>>
Once you group 'a', it goes out of scope (since there's no single 'a'
associated with each group). The reason for the confusing error
message you get is probably that you have another 'a' in scope, which
is indeed inaccessible (most likely, a field with such name in a base
class). Instead, to access the value of the grouping key for each
group, use mg.Key:
>
** * * * * * * * var ActivityByMonths = from a in db.ActivityDatas
** * * * * * * * * * * * * * * * * * * * * * * * * * * * * *where
a.BeginDateTime >= From && a.BeginDateTime <= To
** * * * * * * * * * * * * * * * * * * * * * * * * * * * * *where
a.SubActivityId == sat
** * * * * * * * * * * * * * * * * * * * * * * * * * * * * *group a by
a.BeginDateTime.Month into mg
** * * * * * * * * * * * * * * * * * * * * * * * * * * * * *select new
{ mg.Key, count = mg.Count() };

On Jul 17, 4:05*pm, Pavel Minaev <int...@gmail.comwrote:
>
>
>>>>>>>
That gives me another question. Because in that case the code only
works if we are dealing with only one year. In my case the period
might be spanning several years. So I need to select both the year and
the month.
>
In the end I display the data in a graph with month and year on the x-
axis and number of activities on the y-axis... so being able to select
both month and year is a must.