Definitely dig into ASP.NET MVC2.
All of our projects are now being developed using ASP.NET MVC2. It's not just highly scalable. It's highly testable as well. Which leads to way better maintainable apps in the long term.
WebForms vs. MVC2 points - (speaking out of experience):
Scalability:
In our company we had a lot of applications using WebForms which then were updated and changed by us as needed by our customers.
I think your customer will be requesting more changes on the application in near future. Making calls to other services, and maybe you'll have to rework parts of the final product to match their wishes.
And with the upcoming Cloud Computing and the Windows Azure platform you'll probably need to keep up with your code.
ASP.NET MVC absolutely supports the concept of being able to scale up your application any time you want.
I remember one of our customers walking up on me asking me for an extension for their app (they have a member management system) and the feature would contain something like a link to export the current view as a csv
file so they could do office stuff with it (mostly serial letters).
It wasn't really a big problem setting that feature up. (took around 2 hours including writing tests) - let's go to tests:
Testability:
Using WebForms
we didn't really have much interest writing tests because it was a pure pain to do so.
I remember writing some tests to have at least some proofs but let's drop that topic.. (:p)
We had tests for our custom classes but we couldn't really test all the EventHandlers within the WebForms.
Our CodeBase is way cleaner and saver to use thanks to this testable environment. I just check out some of the code, modify it, run all the tests and: Oh, it broke on strange behavior! - Let's fix that again. Earlier, I remember sitting with my co-worker debugging and trying to find those bugs for hours.
With ASP.NET MVC2 we are now lacking tests!
We ask all kinds of people (even the non-Web ones) to provide test-cases we could feed into our TestSuite.
And yeah, there are some AJAX-Controls too:
AJAXability:
You asked about AJAX Controls and in conjunction with ASP.NET MVC I highly recommend you to check out Telerik ASP.NET MVC UI Controls.
If that isn't something for you, we also make extensive use of jQuery and jQuery UI
With ASP.NET MVC and the HTML Views, those libraries aren't just a pleasure to use, they just look amazingly beautiful.
There is no random-html-tag-id-value
autogeneration anymore!
But what I like most is: You can finally really re-use your code again.
There is so much more to those frameworks than just that, there is the T4 templating system. Auto-Scaffolding for your ViewModels / DomainModels with the Html.EditorFor()
method and of course there is a great and easy way to use the IoC and DI paradigms.
Assuming that you have asked the question with mostly .NET Framework related tags, you'll probably stick with it.
Just to keep the post complete, there are also other frameworks that are just as good (or even better):
And many many more!