Why am I forced to rebuild my project to see changes made to controllers in ASP.NET MVC?

I'm using ASP.NET MVC 3 Beta and for some strange reason, if I change a controller's action and load the action in a browser, it doesn't recompile the assembly to incorporate the changes made. Maybe I'm spoilt from how things were in ASP.NET Webforms, where there was dynamic on-the-flycompilation of code-behind files, but I think this should be possible.

I'm left wondering if maybe it's due to how my project is set up. I'm using VS2010 and compiling for 64-bit executables.