Question

I’m looking for a good way to add arbitrary properties to the objects in a strongly typed list, based on the principle that I shouldn’t pass a DataTable from my business layer to my presentation layer.

For example, I might have a Category class with the properties CategoryId and Title. On one page I would like to fetch a list of all categories (ie. List<Category>) together with the most expensive product in each category.

A while ago, I would have just returned a DataTable with some additional columns in it with the product data in, but I’m trying not to do that — it would be trivial to set up it’s not good practice.

One option is to add a MostExpensiveProduct property to my Category class, but I might want to display the most recently added product in another case, or the cheapest product, so I’d end up adding a lot of properties to cover all the options. This just doesn’t feel right to me.

Am I missing a trick here? What is the best way of doing this? Or should I just be returning a DataTable to which I can add as many columns as I need and not worry about it?

Answer 1

The issue seems to be you have a lot of different views you’d like to offer the user. The options I see are:

• You could construct separate classes for each view that inherit from the Category class. Code gen would be a good solution here.
• You could store an Attributes property, which has an IDictionary interface, and refer to items by key. I’m becoming a fan of this approach.
• You could generate a data table only for binding purposes, for these views… or develop a data table like component where you can refer to fields by Key…
• For fields that you compute (say you store sales tax and net price, and compute gross cost), you could store as a method of the Category object, or as an extension method.

I’m sure there are other options that I haven’t thought about…

HTH.