Most of my first job out of college was spent doing desktop development, some of which was in VB6. I didn't love it, but it was easy to learn. When this button is clicked, that function runs in response to it. Easy.
The controls-and-event-handlers model combined with the language also made it exceptionally easy to create a tangled pile of misplaced responsibilities, but I think you've got to experience that kind of pain before you can see that alternatives even exist. Once you've felt the pain, you can better-evaluate which guidance is actually going to be helpful.
WebForms Was Designed for Desktop Developers
Right around that time, .NET was released. ASP.NET WebForms shared little with classic ASP. The primary goal was to let desktop VB developers make a smooth transition to both .NET and web development at the same time. With that goal in mind, WebForms provided a similar controls-and-event-handlers model. Making a web app felt like making a desktop app.
In order to support that approach, WebForms had to make the stateless world of HTTP feel stateful. View State, the Page Life Cycle, and event handlers allowed the developer to go through the familiar motions of dropping controls onto a designer and wiring up methods to control events, all while ignoring everything that was actually happening.
Abstractions leak, though, and this was a huge abstraction. It helped me get over the initial hurdle to get a web app up and running, but I found the code I wrote was suspiciously like the desktop VB6 mess I'd wanted to grow beyond. I was frequently surprised by the effects of the Page Life Cycle, and every time that happened I had to learn a little bit more about how the abstraction worked under the hood:
"Oh! There's a Big Honking <form> Tag for the whole page, and it contains an Enormous Encoded <input> Tag containing the current state of all the controls, so whenever I need to hit a button click handler I'm really submitting a normal HTML form and then…"
Ugh. Eventually, you just have to know what HTML and HTTP are, even when using WebForms, so the abstraction was no longer helping.
Many Page Life Cycles Later...
While working for a previous employer, ASP.NET MVC came out. We wanted to try out the new approach, and the timing coincided with a new project that was starting up. However, there wasn't much guidance available yet on how to do it well. We were challenged at first by the lack of View State, and in order to keep our old "stateful stateless web" habit going we ended up storing a lot of things into the user's session object. We also kept treating controller actions like they were event handlers, leading to some awkward-looking URLs. Distracted by these initial pains, our controllers started absorbing responsibilities like a sponge. Actually, our controller started absorbing responsibilities - there was only controller in the whole app!
I was writing a lot of controller actions like this:
What I saw was the same thing I saw in WebForms development. The Controller was the new Code Behind, and I was underwhelmed. WebForms's Page Life Cycle and View State hurt, but the real daily pains came from working with classes that were growing out of control, and I was seeing the same thing with my MVC code. It seemed like the abstractions were lighter-weight, and it felt right to work with HTML more directly, but I was definitely missing some guidance.
Turning the Corner
Several coworkers got to take an MVC Boot Camp course at Headspring, and I got to learn by osmosis from them upon their return. At last, I had a good picture in my head of what it looks like when you've succeeded with these tools. Our controllers started to get much more lean:
I started to see how the Onion Architecture, dependency injection, model binders, AutoMapper, and the like help you to keep your controllers small. MVC wasn't a silver bullet; its primary benefit compared to WebForms was that you could make it get out of the way so you could actually start laying down a solid architecture.
ASP.NET MVC has been around for a few years now. Community contributions like MvcContrib helped to motivate change in subsequent releases, and now ASP.NET MVC is legitimately open-sourced. Better-yet, guidance on how to do this well has had years to mature.
MVC is a sharper tool than WebForms. It acknowledges the reality of web technologies like HTML and HTTP, while providing some reasonably-sized abstractions on top of that, such as routing and model binding. Having a better tool in your toolbelt isn't enough, though. You have to see what it looks like when used correctly.