This unique ASP.NET Core book will fill in the gaps in your REST API and backend designs. Learn how to build robust, maintainable, and flexible apps using Gang of Four (GoF) design patterns and modern architectural principles. This new edition is updated for .NET 8 and focuses exclusively on the backend, with new content on REST APIs, the REPR pattern, and building modular monoliths. You’ll start by covering foundational concepts like REST, the SOLID principles, Minimal APIs, dependency injection in .NET, and other ASP.NET Core 8 mechanisms. Then, you’ll learn to develop components using design patterns, including many from the GoF. Finally, you’ll explore organizing your application code with patterns that vary from layers to feature-oriented vertical slice designs, covering CQS and a deep dive into microservices along the way. A brand-new e-commerce project at the end of the book will tie it all together. This how-to guide will teach you how to assemble your own APIs from building blocks, to suit whatever real-world requirements you may have.