写这篇博文的目的就是方便后来者能够在百度里轻松搜到。
反正我找了半天没找到关于.vs目录的介绍，最后还是在同事的帮助下才找到的。
参考地址：https://developercommunity.visualstudio.com/content/problem/82249/vs-folder.html
介绍：
Thank you for your feedback. We have determined that this issue will not be addressed in the upcoming release.
.vs folder is required by Visual Studio to store opened documents, breakpoints, and other information about state of your solution.
We will continue to evaluate it for future releases. Thank you for helping us build a better Visual Studio.
用VS2017打开老的项目时也会产生这个目录。