Hi @Hu, Chuntao Stephen , which version of Visual Studio and TFS are you using? In order for us to investigate it further, could you tell me what changes you made for “Make sure no file is checked out, which means there is no file appearing in the pending changes list of Team Explorer window”?
I've run into this same problem very frequently since our team move to TFS from SVN. It seems to happen somewhat randomly. I've noticed it most commonly when making changes to the project's properties. This is happening on several of our projects. Usually clicking "OK" and then saving again is enough to move on. Mostly it's an annoyance, but I'd like to figure out how to stop the message from appearing.
I forgot to mention, we use Microsoft Visual Studio Professional 2019 Version 16.11.21. I'm uncertain of the TFS version, but would be willing to look if up if you can provide instructions on how to do so.