试图在Linq中做一个子查询...有问题!

尝试:

from p in Periods
group p by p.StartDate.Year into g
orderby g.Key
select new
{
g.Key,
Hours = (from t in Times where t.TransactionDate.Year == g.Key select t).Sum(t => t.Units),
Invoices = (from i in Invoices where i.CreatedDate.Year == g.Key select i).Sum(i => i.Price)
}