In the competitive world of software development, having a good API is simply not enough to captivate your user base. To truly stand out, you must deliver an exceptional Development Experience (DevEx). This session will introduce you to six powerful Roslyn extensibility APIs that can help you elevate your library's usability to new heights. You will learn how to report warnings and errors into the developer's source code in real time, suppress compiler or third-party warnings, and craft code fixes or refactorings. We will also explore advanced techniques for generating source code in real time. Whether you want to attract new developers to your product or take your internal team's productivity to the next level, this talk will provide you with the critical insights you need to make developers feel like your library has always been an indispensable part of their toolkit. Join us to learn how to take your DevEx to the next level.