Returning data from the business layer to the presentation layer

Question

I am developing an ASP.NET 2.0 website. I have created data access and business logic layers. Now in the presentation layer I am returning data from the business layer as a dataset.

My question is whether to use a dataset or object collection (for example a Category object representing the Category table in my database). I have defined all classes that are mapped to database tables (Common objects). But there are situations where I need all of the records from the category table in the presentation layer. I am just confused. What should I do?

Answer 1

I've used both methods depending on the situation. If you only need to display the data from a table in a grid, the dataset(or datatable) method isn't terrible because if fields are added to the table they will automatically appear in the grid...assuming you are auto populating the grid with the columns. I look at this method as more of the quick and dirty method.

Answer 2

I would not return datasets at all. You are tightly coupling you service to you database. In the future when you database evolves you will be forced to change anything that uses the datasets. You want to create an abstraction layer between the database and the service.

Answer 3

I would recomend returning objects or IEnumerable/IList etc of objects.

Depending upon your DB access you can populate a list of category objects manually or using something like LINQ2SQL or ADO.NET Entity framework very quickly, and if required cache them.

Answer 4

You don't want to return datasets, you want to return objects.

Generally when you have a data access layer and a business logic layer you will also want to have an entity layer. The entity layer will be an in memory repersentation of the database result set. If you return one row from the database you load one entitiy object. If you return more than one row, you will load an entity for each row, and return a collection of entities to be consumed by the presentation layer.

If you're using .net 2.0 and above for example, you can create generic collections of the entity type and easily bind different types of controls to these collections.

Hope this is helpful for you.

Answer 5

I'd go with an object/collection solution. So if you are returning one row from a table you have one object, if you are returning several you'd use a generic collection. Generic collection will avoid a boxing/unboxing hit.

[edit]seems I was beaten to it[/edit]