When I began looking at writing the bot for my stream, as with any project I start on, I first started by reinventing a wheel. If you're after a full featured, feature rich bot library with deep Twitch interactivity, written in C#, then I recommend TwitchLib. If you're after the basic shell of a bot, that hasn't solved 90% of the problems yet, then take a look here.
Library contains the core of the project, TwitchStreamBot is the core of everything.
Core library for building up configuration
Some basic functionality to provide examples of how you might build up commands when using the bot code.