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 attemp
Rename the solution's corresponding .SUO file. The SUO file contains the TFS status (online/offline), amongst a host of other goodies.
Do this only if the "right-click on the solution name right at the top of the Solution Explorer and select the Go Online option" fails (because e.g. you installed VS2015 preview).
I am using Visual Studio 2017 15.4.0 version. Especially when i started use lightweight solution option, this offline thing happened to me. I tried to above solutions which are:
Then from File -> Source Control -> Advanced -> Change Source Control. I saw my files. I select them and then chose bind option. That worked for me.
I searched for the solution online and found this solution but wasn't too keen on the registry change.
I found a better way: right-click on the solution name right at the top of the Solution Explorer and select the Go Online option. Clicking this allowed me to select the files that had been changed when I was offline and make the solution online again.
After finding the solution, I found the following msdn forum thread which confirmed the above.