I'd say youtube, assignments and courses.
Also if you're looking for courses check out https://teamtreehouse.com/ it costs sure, but it's pretty good i've used it for a while now also.
If you don't want to pay, you can get trial from them, and then later pay, or if you're not looking to pay any cents in future for courses, you would want to check these out also -
https://www.sololearn.com/Course/CSharp/
Learn C# - Free Interactive C# Tutorial