Every year since PDC09, I had dug up some code that I had originally wrote in 2009, patched it to grab the latest developer event, and then forget about it for another year.
A few years ago, I uploaded a CLI based tool to GitHub that would download sessions from the Build 2015 conference. In 2016, I added parameters to make it grab all items on Channel9 with an Event RSS feed. In 2018, I encountered some issues: first with the RSS feed then with some other oddities stemming from the previous approach, which had more or less in place since 2009.
You can grab the code on GitHub and get all the Build 2018 sessions, change the parameters to grab content from other events, and even contribute some code to add features you’d like to see added.
Get all the session videos from Build 2018
SessionDownloader.exe C:\Downloads\ https://s.ch9.ms/Events/Build/2018/RSS
Get all the session videos from Build 2017
SessionDownloader.exe C:\Downloads\ https://s.ch9.ms/Events/Build/2017/RSS
Get all the session videos from Build 2017 in audio format only
SessionDownloader.exe C:\Downloads\Audio\ https://s.ch9.ms/Events/Build/2016/RSS mp3