Hi,
Well, when I was using latest version of the sandcastle, I discovered that I can reference the sample code which are located in separated file(s) and more then that, I can have many different examples in one file which are separated by region.
So I figured why cant I combine my tests along with documentation. This will grantee that all my samples works.
As far as project, I used TFS before too, but I find that subversion in that case is much more convenient to use, may be its a personal preference I guess. So if you want to contribute sample, tests or both then I can add you as a developer in the project and you could check in code directly. The only thing I would ask you is to use subversion since TFS adds some additional information to project and solution files and directories.
I am not sure if its possible to find parent-child projects on codeplex but I guess I would be curios to know it myself.
If you like, you can contact me on Skype where my nick is olegkap and we can discuss more.
Thanks,
Oleg