title: Is there any website which provide implementation details of ASP.NET Core source code?
body: <p>As ASP.NET Core is open source, I am looking for website which provide source code implementation of various classes and its functions/method. 
  I have seen such website during PluralSight course but I am not able to recall it. I know I can download git hub repo and check source code but I want Website where I can utilize tree like structure to view source.</p>