So basically I asked this question while back:
The query contains references to items defined on a different data context
But this time I am doing it in EF. Does EF supports cross joining between two tables?
You can't do joins between different data context's. You would have to do the join with linq-objects
var crossJoin = from a in context.TableA.AsEnumerable()
from b in context2.TableB.AsEnumerable()
select new
{
a,
b
};