Systems software must be written in C, with unsafe pointers, manual memory management, and the associated cuts and bruises. Or so common wisdom says. This isn't as true as it once was, thanks to the confluence of many trends on both client and server: mobile, constant connectivity, and new trends in isolation like containers. The truth is, with the right discipline, you can reap the productivity, safety, and reliability benefits of using a managed language like C#, while still having great performance and scale. In this talk, I will share some of my key experiences from building an entire operating system in a C# dialect, with a focus on areas like garbage collection, low-level code quality, and dealing with errors and concurrency robustly. Although the patterns and lessons transcend any one language, examples will focus specifically on using the open source C# and .NET projects as they exist today.