APIs are at the heart of modern software development, enabling seamless communication between applications. In the C# and .NET ecosystem, mastering API development is key to building scalable, reliable systems that meet both client and enterprise needs. Written by C# and .NET experts Jesse Liberty and Joseph Dluzen, this book draws on their extensive experience as hands-on programmers to equip you with the tools, techniques, and best practices for creating powerful APIs. Starting with API fundamentals, it covers everything you need to design, build, and consume APIs using .NET technologies such as ASP.NET Core, and explores both controller and Function API implementations. You'll integrate essential tools such as Postman for testing to streamline your development workflow. Through practical examples and exercises, the book guides you from database creation to deploying APIs on Azure. By the end of this book, you’ll have gained real-world skills to develop secure, high-performance APIs that scale with your applications for both personal projects and enterprise-level systems.