entity framework进行一对多的联合查询

 1 using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
 2 {
 3     ObjectQuery<SalesOrderHeader> orders = AWEntities.SalesOrderHeader;
 4     ObjectQuery<SalesOrderDetail> details = AWEntities.SalesOrderDetail;
 5 
 6     var query =
 7         from order in orders
 8         join detail in details
 9         on order.SalesOrderID
10         equals detail.SalesOrderID into orderGroup
11         select new
12         {
13             CustomerID = order.SalesOrderID,
14             OrderCount = orderGroup.Count()
15         };
16 
17     foreach (var order in query)
18     {
19         Console.WriteLine("CustomerID: {0}  Orders Count: {1}",
20             order.CustomerID,
21             order.OrderCount);
22     }
23 }
24 
25