GraphQL in C# (.NET): Building Modern APIs

The book "GraphQL in C# (.NET)" is a practical guide for developers who want to master a modern approach to building web APIs using GraphQL in the .NET ecosystem. Unlike traditional REST services, GraphQL allows clients to request only the necessary data, significantly improving performance and interaction flexibility.

What is this book about?

The author consistently guides the reader from the basics of GraphQL to building full-fledged production solutions on the .NET platform. The main focus is on the Hot Chocolate library — the most popular tool for implementing GraphQL in C#. You will learn:

• How to set up a GraphQL server based on ASP.NET Core.
• Principles of building schemas, types, and resolvers.
• Working with queries (Query), mutations (Mutation), and subscriptions (Subscription).
• Integration with Entity Framework Core and other ORMs.
• Performance optimization: batching, data loaders, caching.
• Error handling, authentication, and authorization.
• Testing GraphQL APIs and documentation.

Who is this book for?

The book will be useful for:

• Junior and Middle C# developers who want to expand their stack with modern technologies.
• Backend developers transitioning from REST to GraphQL.
• Full-stack engineers wanting to understand how to efficiently organize client-server interaction.
• Team leads and architects evaluating the adoption of GraphQL in existing projects.

For comfortable reading, a basic knowledge of C# and ASP.NET Core is sufficient. No experience with GraphQL is required — all concepts are explained from scratch.

What will you learn?

After reading the book, you will be able to:

• Develop flexible APIs that adapt to client needs.
• Avoid the problems of over-fetching and under-fetching data.
• Build complex graph queries with filtering, pagination, and sorting.
• Integrate GraphQL with an existing .NET architecture.
• Cover APIs with tests and document them using GraphQL Playground.

The book contains many practical examples, ready-to-use code, and best practices from the .NET developer community. This is not just theory — you can immediately apply the knowledge gained in real projects.

GraphQL in C# (.NET) is your guide to the world of modern, fast, and convenient APIs. Whether you are building microservices, a monolithic application, or a mobile backend, this book will help you reach a new level of development.