I had my solution in Visual Studio 2012 (which is under TFS source control) open and the TFS server (2010) was down. When I then made a change to one of the files and attempted to save it I got a prompt to ask whether I wanted to Overwrite the file saying the TFS server was down (can't remember the exact words) and the following message appeared in the Output window:
This solution is offline. [Team Foundation Server: http://tfs1:8080/tfs/server]
The solution was offline during its previous session and will remain offline.
How do I get the file change to be recognised as being among Pending Changes and the whole solution back online?