First of all don’t expect to memorize everything in your head. There is way too much to remember. The best way to retain knowledge isn’t to take notes. (Unless you have a great memory this probably isn’t the best path) its learn by doing.
You can read a whole book on .NET technologies (or anything) but if you don’t write a single line of code yourself, odds are your going to forget, or have a tough time using that knowledge in practice. The main reason is you learn through failure, and you can’t fail taking notes.
If I gave you a project and a 1 month deadline, and you spent the entire month struggling through the code, debugging your code, hitting 5 thousand brick walls and didn’t finish the project in the 1 month, but stayed active, and grinded against the code the whole time, you would learn a hell of a lot more than if you spent 1 month reading about everything possible related to the project.
I purposely didn’t specify what the project was is because it doesn’t matter, the idea is the same regardless. You learn more through doing because you hit the brick walls, because you spend 15 mins debugging, because you screwed up
So yes, you can take notes, but I wouldn’t use that as a main focus. Especially if you plan on using things you read about, you should take a more proactive path. Personally I do the following:
If I want to possibly use something directly in the future, I try it out in a side-project. This means taking what I know, and building out a project more or less from scratch, with as close to a “real” scenario as possible.
If I’m more curious and just want to know about new technologies (hello redux, clojure and web assembly!) I’d read articles on the topic, but not much more. I’d expect myself to have to dig deeper later if I do want to know more about these topics. As I said, it’s fine to look things up, if need be.
If I straight up don’t understand a concept, then I’d brain storm around it, think about things in different angles (This is what I took to finally understand service-workers). Something complex that might not make sense immediately are usually complex topics like algorithms, or fancy technologies. These sorts of things might be great candidates for note taking, but since these concepts are usually complex, you probably need to think about it, and can’t just jump right in.
Finally its great to stay in the loop, so following feeds (rss, twitter, other) are great to hear about new things and expand your horizons, just don’t expect to learn everything and anything, and memorize it all. Learn what is out there to learn but focus on what you will need sooner rather than later.