编写复杂的Linq2SQL查询

Question

I have Following Data

Category

• CategoryName
• CategoryID

Product

• ProductID
• ProductName
• CategoryID

Item

• ItemID
• ItemName
• ProductID

What will be the query so that i will get multiple list ie

ListOfCategory contains CategoryName and ListOfProduct<>

ListOfProduct contains ProductName and ListOfItems<>

ListOfItems<> Contains ItemName and 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 });

I know this is so wrong, So Kindly Help me

Answer 1

you can use sub queries in Linq to simplyfy your requirement.

//get the list of items with all details

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();