如果在不连接TFS的情况下，编辑一个已经source control的solution，总是会有烦人的提示信息。如果你确定不再需要source control，可以这么干。
Here is how to remove this association:
1. Remove all *.vssscc and *.vspscc files from your Solution folders.
2. Check if your Solution *.sln file is Read-Only. Remove this flag if needed.
3. Open *.sln file in an editor. I prefer Windows Notepad for such operations.
4. Find GlobalSection(TeamFoundationVersionControl) looking as showing below and remove it begining with GlobalSection and ending with EndGlobalSection:
GlobalSection(TeamFoundationVersionControl) = preSolution
SccNumberOfProjects = 2
SccEnterpriseProvider = {4CA58AB2-18FA-4F8D-95D4-32DDF27D184C}
SccTeamFoundationServer = http://<YourTFS>/tfs/defaultcollection
SccLocalPath0 = .
SccProjectUniqueName1 = <Your Project path and name in TFS>.csproj
SccProjectName1 = <Project Name>
SccLocalPath1 = <Project Path>
EndGlobalSection
5. Save and close your Solution file.
6. Go ahead and open this Solution in Visual Studio IDE as usual.
7. If you will get IDE warning similar as shown below, just select "Permanently remove source control association bindings".
That's it! Now you can associate your code with a new TFS Project.
P.S. I tested this on VS/TFS 2010/TFS2013. Not sure if this works with older versions.