I found that sometimes when I use "compare" in Visual Studio, I couldn't edit the local version at all. But sometimes it does allow this. Is there any setting in TFS that is related to this functionality?
The steps I followed: Right clicked the file in Solution Explorer I want to compare, and chose "Compare", with the dialog window popped out like this:
and cliked "OK"
I found several questions similar to my question, but amazingly all of them don't have even a relevant answer:
Visual Studio Diff Tool - When is Editing Allowed?
Under what conditions will the Visual Studio 2012 Difference Viewer allowing editing a source file