Entity Sql Group By problem, please help

help me please with this simple E-sql query:

var qStr = "SELECT SqlServer.Month(o.DatePaid) as month, SqlServer.Sum(o.PaidMoney) as PaidMoney FROM XACCModel.OrdersIncomes as o group by SqlServer.Month(o.DatePaid)";

Here's what I have.

I have simple Entity called OrdersIncomes with ID,PaidMoney,DatePaid,Order_ID properties

I want to select Month and Summed PaidMoney like this:

month  Paidmoney

1 500

2 700

3 1200

T-SQL looks like this and works fine:

    select MONTH(o.DatePaid), SUM(o.PaidMoney)
    from OrdersIncomes as o
    group by MONTH(o.DatePaid)

results:
-----------

3           31.0000

4           127.0000

5           20.0000

(3 row(s) affected)

but E-SQL doesnot work and I dont know what to do. here my E-SQL which needs refactoring:

var qStr = "SELECT SqlServer.Month(o.DatePaid) as month, SqlServe开发者_如何学运维r.Sum(o.PaidMoney) as PaidMoney FROM XACCModel.OrdersIncomes as o group by SqlServer.Month(o.DatePaid)";

there's an exception: ErrorDescription = "The identifier 'o' is not valid because it is not contained either in an aggregate function or in the GROUP BY clause."

if I include o in group by clause, like: FROM XACCModel.OrdersIncomes as o group by o then I don't get summed and aggregated results. Is this a bug, or what I'm doing wrong?

Here's a Linq to Entities query and it works too:

var incomeResult = from ic in _context.OrdersIncomes
     group ic by ic.DatePaid.Month into gr
     select new { Month = gr.Key, PaidMoney = gr.Sum(i => i.PaidMoney) };

Give an alias name to the Group By clause and use that alias in the select clause.

SELECT PaidMonth, SqlServer.Sum(o.PaidMoney) as PaidMoney FROM XACCModel.OrdersIncomes as o group by SqlServer.Month(o.DatePaid) as PaidMonth