mojoportal uses pre-compiled codebehind via the VS 2005 SP1 Web Application project type not the Web Site Project type which uses the compilation model you are apparently expecting.
Deploying C# source code on the server has no effect, it will use the compiled dlls in the bin folder regardless of what you change in source. If you want your change to take effect you must compile and redeploy the dll.
The only on demand compiling for this project type is the JIT compilation from msil to native code, it does not compile C# on demand in this project type.
It debugs just fine in VS 2005.
Hope it helps,
Joe