I've found what I believe to be a bug in ASP.NET MVC's caching model inasmuch as it appears to be caching GET's when caching is not specified. However, even though I think that it's a bug it's way more likely that this is something that I haven't understood or something that I've done wrong: The first rule of programming: It's my fault.
I've written a wizard style registration process for a site. It's fairly simple and stores the stage at which the user is at in a session state variable. Here is the code:
public ActionResult Register()
string registerStage = GetStage();
return View("Register2", UserDetailsVM);
return View("Register3", UserDetailsVM);
What I found was that without the [OutputCache(Duration=0, VaryByParam="None")] attribute it appeared that the view was being cached.
If I removed this attribute and called the action via a browser it would work and break points inside the action would be hit the first time I navigated to the action/page. If I then navigated to a web form page (this is a hybrid web form / mvc application) and then returned to this page the Register action would not be hit. Added the [OutputCache(Duration=0,...] fixed the problem.