I am using Visual Studio Professional 2010 and the Team Foundation Server Express (beta). My VS Project (C#.Net / WPF) has been migrated from VS 2008 (without TFS) to VS 2010 (with TFS).
Whenever I apply changes to my code and try to debug my application, I get messages like This breakpoint will not be hit. (in german: Der Haltepunkt wird momentan nicht erreicht. Der Quellcode weist Unterschiede zur Originalversion auf.) and the project is started using the old executable version (the one with the last successful build). No errors occure, the code is OK, but the changes are not applied either.
When I manually cleanup and rebuild my project, everything works quite fine - but there has to be a fix for this issue?
Edit: I just added a new project to my VS solution and checked it in on the TFS Server. Using this new project the problem does not occure. Even when I add the same dependencies I used in the project mentioned above, the debugging and building of the new project works fine without the errors mentioned above.
Maybe this information helps you to lead me to a solution.
It's not clear whether existing answers are not sufficient. I can't know exactly what's causing your problem; but, I can detail some places this potentially comes up.
The first area that I commonly see this is when a project references an assembly directly. You can create a project that creates an assembly. Another project might use that assembly and you can reference by assembly directly (and not add a reference to the "project"). This disconnects VS from really knowing it needs to "build" that referenced assembly first and it will sometimes get out of sync with the debugging symbols (PDB). You can tell if a project has been referenced or an assembly has been referenced in the properties of the reference (expand References in Solution Explorer, right-click a reference, and select Properties). A referenced project will not have a Specific Version property, while an assembly reference will. You can sometimes also tell from Project\Project Dependencies. If you have a reference to an assembly generated by another project but that project isn't a dependency in Project Dependencies, it might be an assembly reference. To fix this, you can usually just delete the reference and add a reference to the project.
I've also find that sometimes breakpoints confuses the debugger. If I have many breakpoints or they've been kicking around a long time, the debugger sometimes does some weird things. If I delete all the existing break points (Debug/Delete all breakpoints) and re-apply them the debugger is usually much happier.