I believe I have a very good understanding of programming logic fundamentals (passing around variables, nested conditional statements, etc). I am currently going through a book on ASP.NET and am pretty much lost on all the Page Rendering Model, Custom Rendered Controls, Composite Controls, etc. I understand how to use the standard controls no problem. Do I really need to understand all those other things to become a junior developer? Any advice is appreciated!
A Junior Developer needs to have the basics down. In your field, that would include a pretty firm grasp on OOP, the layout of ASP.NET applications, master pages, code behind (whether it be C# or VB.NET), etc. Basically the stuff you can pick up with personal projects. Everything else is just gravy.
The specifics, like composite controls and page rendering will be picked up and mastered while actually utilizing the certain technology. Nobody is going to expect you to walk in the front door and be a master with ASP.NET. You are young and your experience dictates that. Even the best developers aren't born knowing this stuff. They know it because they've used it....for many, many years.
BUT MOST IMPORTANTLY: Just be willing to learn and listen to the mid-level and senior developers.
I think as a Jr Developer (I am one) you should be where you are at; solid knowledge of fundamentals, eagerness to learn and an open mind. You will consolidate your skills as you are introduced to new problems to solve. I think technology-specific skills are developed and learned on the job, at least that's what I've found. Good luck!
The truth is: it depends on company and on the meaning of junior position. Sometimes junior is equal to graduate and sometimes junior is above graduate.
Some companies expects that you know what ASP.NET is. Some companies expects that you know what .NET and C# is and some companies expects that you know what HTTP and web development is.
If junior = graduate you can find companies where simple diploma from information technology related is enough (= theoretical knowledge) and company will teach you what they need. It doesn't mean you don't have to learn yourselves - self learning is the most important part of your career development.