博问 / 全部问题 / .NET技术 / ORM

今天试验Entity Framework 遇到问题，不知道向下面这些Lambda 表达式 为何会报错。
又该如何修改。

NORTHWND.MDFModel.Entities ee = new NORTHWND.MDFModel.Entities();

            var a = (from o in ee.Orders
                    join c in ee.Customers on o.Customers equals c
                    join s in ee.Shippers on o.Shippers equals s
                    where c.CustomerID == "ALFKI"
                    select new{c.CustomerID,c.CompanyName,o.OrderID,ShipperCompany = s.CompanyName}
                    ).FirstOrDefault();