Hi,
The referenced DLLs are not added to source control because they are not a part of the project.
Generally, we build DLLs for each project and put them together for executing. If you really need to add the DLL with the project, you have to add it to the project, so that it go with the whole project and can be checked into the source control.
HTH. If this does not answer your question, please feel free to mark the post as Not Answered and reply. Thank you!
Sincerely,
Kevin Yu
Microsoft Online Community Support
Please remember to click ?Mark as Answer? on the post that helps you, and to click ?Mark as Not Answer? if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.