Web Site Projects vs Web Application Projects

For web development, Visual Studio 2005 (VS 2005) supports two project options: Web Site Projects (WSPs) and Web Application Projects (WAPs). The earlier was built-in with the initial release of VS 2005, the latter were introduced later and are included on the VS 2005 SP1.

WSPs are leveraging the very same dynamic compilation system used by the ASP.NET 2.0 at runtime; when using this option, you don't need a project file (you just need to follow some easy and intuitive folder conventions).

WAPs are leveraging the MSBuild buld system, and when using them, all the code in a project is builded in a single assembly; when using this option, you do need a project file.

There are various pro and cons for each of those models, but if we focalize just on the speed of the build, the WAP option wins hand down every time you build from scratch or rebuild.

Why?

The main reason, as explained from Scott Guthrie, is that with the WAP, only the code-behind and the /app_code/* classes are built, while with the WSP the ASP.NET runtime spend its time analyzing and compiling each ASP.NET related code (content/controls/inline code).

Monorail case:

First and foremost, having a MSBuild capable project, as in the WAP option, helps when you have to integrate your projects with tools like CruiseControl.Net. Now, it is possible to do that also for the WSP option, but it is not as neat.

Second, using Monorail, the amount of ASP.NET pages in the web projects is probable negligible (usually just 1, quite trivial in every chances, which is left there to "fire" the build on certain circumstances), so there is not really any reason to use the deep verification features of the WSP model: there are not ASP.NET related file to build.

From experience and from investigation, I can add that on the web there are various tips and tricks to speed up the WSP, but the point is that as much as you can speed up a WSP build, the main target of this kind of exercise is to make it as fast as a WAP build.

Conclusion:

On non trivial web projects, and when you don't need deep verification of ASP.NET related files, use ever the WAP option.

p.s.: I shouldn't add this, but really, don't use the /app_code folder under almost any circumstance. Put your logic in different layers (VS class projects), and if really you need to use the /app_code folder, leave there only very stable classes.