编写复杂的Linq2SQL查询

Question

我有以下数据

类别

• 分类名称
• 分类ID

产品

• 产品编号
• 产品名称
• 分类ID

项目

• 物品ID
• 项目名称
• 产品编号

什么是查询，以便我将获得多个列表，即

ListOfCategory包含CategoryName和ListOfProduct <>

ListOfProduct包含ProductName和ListOfItems <>

ListOfItems <>包含ItemName和ItemID

 var cats = (from g in CMP.tblCategories
                        join proc in CMP.tblProducts
                        on g.CategoryID equals proc.CategoryID
                        join item in CMP.tblItems
                        on proc.ProductID equals item.ProductID
                        select new { Cat = g.Name, Pro = proc.Name, Itm = item.Name, ItmID = item.ItemID });

我知道这是错的，所以请帮帮我

Answer 1

您可以在Linq中使用子查询来简单地满足您的要求。

//获取所有详细信息的项目列表

var Items = (from g in CMP.tblCategories
                        join proc in CMP.tblProducts
                        on g.CategoryID equals proc.CategoryID
                        join item in CMP.tblItems
                        on proc.ProductID equals item.ProductID
                        select new { Category = g.Name, ProductName = proc.Name, ItemName = item.Name, ItemID = item.ItemID });

//Group by ProductName  to get a list of ProductName , List<Items>

 var Products  = (from i in Items
                   group i by i.CategoryName into g
                  select new { CategoryName = g.Key, 
                         Products = (from p in Items
                                    group p by p.ProductName into Productgroup
                                     select new {ProductName = Productgroup.Key,              Items = Productgroup})
}).ToList();