EmEditor Professional can completely replace the Windows built-in Notepad, developed by Japanese Emurasoft Inc, it's famous for lightweight, agile and its powerful, rich. So that hold many users' high praise. Originally released in 1997, and is still in the sustainable development.
Concerning the powerful, super cool and perfect functions of Sublime Text, I believe what you know is not less than mine, here we do not introduce its various features any more. I just like to call it the only coolest code editor candystar for programmers.
All these license keys were tested (on 04/29/2017) working all right (and universal) for Sublime Text 2/3 (tested working: Build 2221; Build 3062~3131) on Windows, Mac OS X and Linux platforms. Just choose any one legal registration code below and paste it into your "Enter License" panel to complete the registration.
IDM Computer Solution's UltraEdit claims to be the #1 and simply the world's best text editor in the world. Actually this's relative, just as a lot of reviews for some great software you can see in AppNee - most of which depend on personal use experience and habits. Anyhow, we can't deny that UltraEdit is really powerful.
For learning or formal development of C#, there are only two best IDE for choice at present: either the 10+ GB size of Visual Studio or SharpDevelop with only 10+ MB file size. The latter is an open-source IDE with layout similar to IDEA for Java and high flexibility & extensibility, which lets a user find everything new and fresh. It never wants to be an IDE that tries to support everything as Eclipse. Instead, it just gives you an interface, and you can do all the rest by yourself.