To help get up to speed on .Net, I'm taking an app I spend a significant portion of time on and rewriting it. I thought it would also be a good idea to learn some better design ideas at the same time.

I didn't write the app in question, I maintain. Clients are offered customizing. The form where the user establishes preferences is where I'm starting. For cusomer requests 2 things happen:

1) One of the pages on a pageframe is totally different depending on the client. For this page a composite object has been designed that is dropped onto this page at runtime.

2) Typically, the other situations are textboxes which have specific validations depending on the client, or different input masks, etc. But the control appears for all clients.

Currently, there is tons of code in the form to modify the behavior for different clients. What are some approaches, or design patterns that I could use to redesign?

thanks,

Pf