Question

Let say I have the following classes:

Product { ID, Name }

Meta { ID, Object, Key, Value }

Category { ID, Name }

Relation {ID, ChildID, ParentID } (Child = Product, Parent = Category)

and some sample data:

Product:

ID   Name

1    Chair
2    Table

Meta

ID   Object  Key     Value

1      1     Color   "Red"
2      1     Size    "Large"
3      2     Color   "Blue"
4      2     Size    "Small"

Category

ID   Name

1    Indoor
2    Outdoor

Relation

ID   ChildID   ParentID

1       1         1
2       1         2
3       2         1

Can we use Distinct and Group by to produce the following format (ProductDetail)

ID=1,
Name=Chair,
Parent=
{
  { ID=1, Name="Indoor" },
  { ID=2, Name="Outdoor" }
},
Properties { Color="Red", Size="Large" }

ID=2,
Name=Table,
Parent=
{
  { ID=1, Name="Indoor"}
},
Properties { Color = "Blue", Size = "Small" }

which we can get the “Color” value of the first item by using

ProductDetails[0].Properties.Color

Any helps would be appreciated!

Answer 1

No, you can’t do this based on what you’ve said – because “Color” and “Size” are part of the data, rather than part of the model. They’re only known at execution time, so unless you use dynamic typing, you’re not going to be able to access it by Properties.Color.

You could, however, use Properties["Color"] potentially:

var query = from product in db.Products
            join meta in db.Meta 
                on product.ID equals meta.Object 
                into properties
            select new { Product = product,
                         Properties = properties.ToDictionary(m => m.Key,
                                                              m => m.Value) };

So for each product, you’ll have a dictionary of properties. That works logically, but you may need to tweak it to get it to work in the entity framework – I don’t know how well that supports ToDictionary.

EDIT: Okay, I’ll leave the above up as the “ideal” solution, but if EF doesn’t support ToDictionary, you’d have to do that part in-process:

var query = (from product in db.Products
             join meta in db.Meta 
                 on product.ID equals meta.Object 
                 into properties
             select new { product, properties })
            .AsEnumerable()
            .Select(p => new {
                    Product = p.product,
                    Properties = p.properties.ToDictionary(m => m.Key,
                                                           m => m.Value) });