left join 一个子查询，这种sql 怎么用linq实现

[antony1029]

select *  
FROM Customer c
 left join(
Select o.CustomerId ,sum(o.OrderTotalAmount) as OrderTotalAmount from  [order] o
group by o.CustomerId
)ot
on c.id=ot.CustomerId

这种sql 用linq怎么实现

[antony1029]

            var q =
   from c in  customer
   join o in _orde  on c.Id
   equals o.CustomerId into orders
   select new
   {
       c.Username,
       OrderTotal = orders.Sum(i=>i.OrderTotal)

   };

[antony1029]

还有其他的写法吗？？

[q107770540]

var query = from c in db.Customer
            join ot in db.order.GroupBy(o=>o.CustomerId).Select(o=>new{CustomerId=o.Key,OrderTotalAmount=o.Sum(x=>x.OrderTotalAmount) })
			on c.id equals ot.CustomerId into lg
			from c in lg.DefaultIfEmpty()
			select c;

[antony1029]

引用 3 楼 q107770540 的回复:

var query = from c in db.Customer
            join ot in db.order.GroupBy(o=>o.CustomerId).Select(o=>new{CustomerId=o.Key,OrderTotalAmount=o.Sum(x=>x.OrderTotalAmount) })
			on c.id equals ot.CustomerId into lg
			from c in lg.DefaultIfEmpty()
			select c;

感谢，非常正确。比我的执行效率要高。