Minimal APIs in ASP.NET 9: Design, implement, and optimize robust APIs in C# with .NET 9

Minimal APIs in ASP.NET 9

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To my wife, Kerrie, and my daughter, Neave. You gave me the strength to write, and you waited patiently for me to finish. I love you both with all my heart.

To Chris, Gemma, and Charlotte, my comrades at NexBotix. Thanks for your encouragement and support throughout the whole process.

– Nick

Contributors

About the author

Nick Proud is a software engineer, technology leader, and Microsoft MVP for Developer Technologies, specializing in robotic process automation and .NET. He is currently the director of software engineering at NexBotix an intelligent automation firm, as well as a technical content creator, producing educational video content about C# and Microsoft Azure.

I want to thank the people who have supported me on this journey, especially my family and colleagues at NexBotix. I also want to thank Peter Bull and Daniel Tallentire for their thorough technical review and the LinkedIn/YouTube community for their continued support of my content.

About the reviewers

Daniel Tallentire is a software engineer and engineering manager with two decades of experience developing SaaS software, using the Microsoft development ecosystem. He has a passion for learning and development and has mentored and coached multiple engineers and managers throughout his career. He speaks on these topics at meetups and conferences. Daniel currently works as an engineering manager at Citation Group, supporting multiple teams in developing software in the HR and employment software fields. In his spare time, Daniel likes to walk the hills of the Peak District, read books, and spend time with his family.

Peter Bull is a Microsoft MVP, software developer, presenter, content creator, and Microsoft technology enthusiast. Peter has over three decades of personal software development experience and more than two decades of professional software development expertise, including web, mobile, and desktop. His journey began with BASIC on the Commodore 64, evolving through every major release of .NET to modern .NET, and beyond! Peter, aka RoguePlanetoid, enjoys sharing what he knows with the community, aiming to mentor new or existing developers and inspire them with his tutorials, talks, and workshops with Tutorialr. He is also an avid content creator who enjoys engaging with the tech community through writing, speaking, and his RoguePlanetoid podcast.

I want to express my gratitude to those who have inspired and taught me throughout my journey as a software developer. Their support and guidance have been invaluable in helping me reach where I am today. In return, I aspire to inspire and teach others, sharing the knowledge and experiences I have gained. My goal is to help others on their own software developer journey by offering the same encouragement and mentorship I was fortunate to receive.

Table of Contents

Preface

Part 1 - Introduction to Minimal APIs

1

Getting Up and Running with Minimal API Development

Technical requirements

Understanding minimal APIs

Contrasting minimal APIs with traditional API approaches

The significance of minimal APIs in modern development

Installing required tools and dependencies

Installing Visual Studio for Windows

Installing Visual Studio Code for Mac and Linux

Configuring development environments

Creating a project in Visual Studio

Creating a project in Visual Studio Code

Summary

2

Creating Your First Minimal API

Technical requirements

Project structure and organization

Endpoints

Models

Routes

Defining endpoints and routes

GET methods

POST methods

PUT methods

PATCH methods

DELETE method

Building the employee management API

Creating the API

Creating the first endpoint

Handling HTTP requests

Summary

3

The Anatomy of a Minimal API

Anatomy of a minimal API

Components of a minimal API application

The API request lifecycle

Summary

Part 2 - Data and Execution Flow

4

Handling HTTP Methods and Routing

Technical requirements

Handling requests

Defining endpoints in the Todo API

Getting todo items

Creating Todo items

Updating existing Todo items

Managing route parameters

Request validation and error handling

Manual validation

Validation with data annotations and model binding

Summary

5

The Middleware Pipeline

Technical requirements

An introduction to middleware

Configuring middleware pipelines

Middleware classes

Inline middleware

Implementing custom middleware

Terminal middleware

Handling errors within the middleware pipeline

Summary

6

Parameter Binding

Parameter binding sources

Route values

Query strings

Optional query string parameters

Headers

Strongly typed object binding

Form values

Explicit binding with attributes

Binding parameters through dependency injection

Binding precedence

Creating custom binding logic

Summary

7

Dependency Injection in Minimal APIs

Understanding DI

The DI container

The case for DI

Configuring DI in minimal APIs

Setting up a scoped DI project

Creating a singleton DI project

DI best practices

Avoiding the service locator pattern

Registering services with an extension method

Using sensible service lifetimes

Summary

8

Integrating Minimal APIs with Data Sources

Technical requirements

Understanding data integration in minimal APIs

Connecting to and integrating with SQL databases

Configuring the connection to the database and retrieving records

Inserting Employee records

Executing database transactions from API endpoints

Connecting to MongoDB

Summary

9

Object Relational Mapping with Entity Framework Core and Dapper

Technical requirements

Introduction to ORMs

Configuring Dapper in minimal API projects

Performing CRUD operations with Dapper

Configuring Entity Framework in minimal API projects

Performing CRUD operations with Entity Framework

Summary

Part 3 - Optimal Minimal APIs

10

Profiling and Identifying Bottlenecks

Technical requirements

An introduction to profiling and performance monitoring

Introducing the profiler

Performance metrics

Profiling tools and techniques

Profiling in Visual Studio

Benchmarking with BenchmarkDotNet

Common performance bottlenecks

Summary

11

Utilizing Asynchronous Programming for Scalability

Technical requirements

Understanding and implementing asynchronous patterns in a minimal API

Task-based asynchronous pattern

TAP with async/await

Asynchronous processing pattern

Common pitfalls and challenges

Summary

12

Caching Strategies for Enhanced Performance

Technical requirements

Introduction to caching in minimal APIs

In-memory caching techniques

Distributed caching strategies

Response caching

Summary

Part 4 - Best Practices, Design, and Deployment

13

Best Practices for Minimal API Resiliency

Technical requirements

Code organization and structure

Exploring folder structures

Feature-based modular structure

Layered modular structure

Design patterns

The factory pattern

The repository pattern

The strategy pattern

Error Handling

Security considerations

Authentication

Authorization

Rate limiting

Summary

14

Unit Testing, Compatibility, and Deployment of Minimal APIs

Technical requirements

Unit testing and integration testing for minimal APIs

Compatibility and migrating minimal APIs to .NET 9

Deploying minimal APIs

Deploying to Microsoft Azure App Service (cloud deployment)

Deploying to a Docker container

Deploying on-premises with Kestrel

Summary

Index

Other Books You May Enjoy

Preface

This book is a comprehensive guide that delves into the world of building streamlined and efficient web services with ASP.NET using minimal APIs.

As the landscape of web development continues to evolve, there is a growing demand for simplicity, speed, and maintainability. I wrote this book to introduce developers—whether experienced or new to the ASP.NET ecosystem—to the power of minimal APIs, an approach that allows for the creation of lightweight and performance-oriented applications.

Why minimal APIs?

With the release of .NET 6 in 2021, Microsoft introduced minimal APIs as a new way to define HTTP APIs with less ceremony and boilerplate code. Minimal APIs focus on reducing the overhead traditionally associated with larger frameworks such as ASP.NET MVC, while still maintaining the robustness of the .NET platform. By stripping away unnecessary complexity, minimal APIs empower developers to rapidly prototype, iterate, and deploy applications that scale with their needs.

In this book, I will walk you through the essentials of minimal APIs, from basic routing and endpoint structure to advanced features such as dependency injection, authentication, and middleware integration.

I’ll also introduce you to some core design principles, providing an overview of some best practices designed to keep your minimal APIs maintainable, secure, and scalable over time.

Each chapter is structured to provide hands-on examples, ensuring that by the end, you’ll not only understand how to use minimal APIs but also why they matter in modern software development.

At the time of writing, .NET 9 had reached its first release candidate phase (RC1), and .NET 9 was very close to general availability. I’ve included information throughout the book on new minimal API features in .NET 9.

Who this book is for

The book is intended to serve as an introduction to Minimal APIs, allowing developers with a basic understanding of C# and object-oriented programming (OOP) to explore the main concepts and begin their Minimal API development journey.

Whether you are an experienced ASP.NET developer looking to leverage new tools or a newcomer seeking to understand web development, this book will guide you step by step. It’s ideal for developers seeking to build microservices, start-ups prototyping new ideas, or even established enterprises looking for a more efficient way to handle specific API needs.

What this book covers

Chapter 1

, Getting Up and Running with Minimal API Development, introduces the world of minimal APIs, helping you to understand their relevance in modern software development and how they differ from traditional API approaches. It also instructs you on how to set up their development environment.

Chapter 2

, Creating Your First Minimal API, introduces the core elements of a minimal API, such as endpoints, models, and routes, before getting you building endpoints using varying HTTP methods.

Chapter 3

, The Anatomy of a Minimal API, delves into more detail on the building blocks of a minimal API, outlining the various components found within, along with an overview of the request lifecycle.

Chapter 4

, Handling HTTP Methods and Routing, focuses on how incoming requests are handled and how this can differ based on different HTTP methods used. It covers the management of route parameters and introduces request validation and error handling in minimal API endpoints.

Chapter 5

, The Middleware Pipeline, explains the concept of middleware in ASP.NET, before instructing you on how you can configure and implement it in the context of minimal APIs.

Chapter 6

, Parameter Binding, discusses the ways in which parameters can be sent into minimal API endpoints. The various parameter binding sources are explored, along with examples of how custom bindings can be created.

Chapter 7

, Dependency Injection in Minimal APIs, introduces dependency injection as a software development concept before exploring its usage in minimal APIs. Best practices for dependency injection are also outlined.

Chapter 8

, Integrating Minimal APIs with Data Sources, helps you understand how data can be integrated into a minimal API, with examples focusing on SQL Server and MongoDB.

Chapter 9

, Objected-Relational Mapping with Entity Framework Core and Dapper, takes the learning points from Chapter 8

further, introducing object-relational mapping (ORM) frameworks such as Entity Framework Core and Dapper. The chapter provides examples of the configuration of the respective frameworks and how they can be used to create CRUD operations.

Chapter 10

, Profiling and Identifying Bottlenecks, focuses on managing and optimizing the performance of minimal APIs. Various profiling tools are explored and we explore several common performance bottlenecks.

Chapter 11

, Utilizing Asynchronous Programming for Scalability, demonstrates the benefits of asynchronous programming in minimal APIs, providing examples of various asynchronous patterns. The chapter also provides examples of common pitfalls and challenges associated with asynchronous execution within minimal APIs.

Chapter 12

, Caching Strategies for Enhanced Performance, takes the theme of performance further by introducing you to caching and its place within minimal APIs. Various caching techniques are demonstrated, using caching technologies such as ASP.NET’s in-memory cache and Redis.

Chapter 13

, Best Practices for Minimal API Resiliency, turns our attention from performance to resiliency, suggesting ways in which code can be structured in a minimal API to encourage long-term functionality. Topics such as error handling and security considerations are also explored.

Chapter 14

, Unit Testing, Compatibility, and Deployment of Minimal APIs, closes out the book with topics related to the latter phases of minimal API development. Unit testing and integration testing are demonstrated using xUnit, specific compatibility requirements are outlined, and there are hands-on examples of how minimal APIs can be deployed to various hosting platforms.

To get the most out of this book

You will need to have a basic understanding of OOP languages and C# to understand the examples in this book. You will also need to have a basic understanding of what an API is, as well as how relational databases such as SQL work.

As .NET is cross-platform, it is assumed that your operating system is either Windows, MacOS or Linux, all of which are compatible.

Readers using MacOS or Linux

For readers on these operating systems, it is recommended that Visual Studio Code is used as an alternative to Visual Studio 2022.

If you are using the digital version of this book, we advise you to type the code yourself or access the code from the book’s GitHub repository (a link is available in the next section). Doing so will help you avoid any potential errors related to the copying and pasting of code.

Download the example code files

You can download the example code files for this book from GitHub at https://github.com/PacktPublishing/Minimal-APIs-in-ASP.NET-9

. If there’s an update to the code, it will be updated in the GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/

. Check them out!

Conventions used

There are a number of text conventions used throughout this book.

Code in text: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: In the Employees table, we have set the Id column as an identity column, meaning that it will be populated by SQL Server on insertion of any record, with the Id value incrementing by 1 on each insert.

A block of code is set as follows:

app.MapPut(/employees, (Employee employee) =>

{

    EmployeeManager.Update(employee);

    return Results.Ok();

});

Any command-line input or output is written as follows:

mongodb://localhost:27017/MyCompany

Bold: Indicates a new term, an important word, or words that you see onscreen. For instance, words in menus or dialog boxes appear in bold. Here is an example: You can do this by going to Tools | Manage NuGet Packages | Package Manager Console.

Tips or important notes

Appear like this.

Get in touch

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