So I’m working on a project with a number of other developers at present. However every so often when another developer adds files to source control when they are added to my local solution they appear unbound to source control and Visual Studio treats them as though they are not bound to TFS.

Note the missing padlock icons on some files. The files missing the padlock were retrieved on my last Get Latest operation.

To ensure that Visual Studio treats these correctly and enforces source control behaviour you have to refresh the source control connection. Ensure that you select the solution file, to refresh all projects, or just a single project to target the refresh at just that project. Then select File > Source Control > Refresh Status or Alt + F, Alt + R, Alt + T for you keyboard jockeys out there.

Lo and behold, padlocks are present and source control behaviour is correct!