I have written an ASP.NET WebForms portal for a client. The project has kind of evolved rather than being properly planned and structured from the beginning. Consequently, all the code is mashed together within the same project and without any layers. The client is now happy with the functionality, so I would like to refactor the code such that I will be confident about releasing the project. As there seems to be many differing ways to design the architecture, I would like some opinions about the best approach to take.

FUNCTIONALITY The portal allows administrators to configure HTML templates. Other associated "partners" will be able to display these templates by adding IFrame code to their site. Within these templates, customers can register and purchase products. An API has been implemented using WCF allowing external companies to interface with the system also. An Admin section allows Administrators to configure various functionality and view reports for each partner. The system sends out invoices and email notifications to customers.

CURRENT ARCHITECTURE It is currently using EF4 to read/write to the database. The EF objects are used directly within the aspx files. This has facilitated rapid development while I have been writing the site but it is probably unacceptable to keep it like that as it is tightly coupling the db with the UI. Specific business logic has been added to partial classes of the EF objects.

QUESTIONS The goal of refactoring will be to make the site scalable, easily maintainable and secure.

1) What kind of architecture would be best for this? Please describe what should be in each layer, whether I should use DTO's / POCO / Active Record pattern etc.

2) Is there a robust way to auto-generate DTO's / BOs so that any future enhancements will be simple to implement despite the extra layers?

3) Would it be beneficial to convert the project from WebForms to MVC?