Programming APIs with C# and .NET: Develop high-performance APIs that ensure seamless application communication and enhanced security

Programming APIs with C# and .NET

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To my 106-year-old mother, my wife, and especially my children. I am a very lucky man.

– Jesse Liberty

To my wife, children, and parents.

– Joseph Dluzen

Contributors

About the authors

Jesse Liberty specializes in C#, Git, and building world-class APIs. He hosts the popular Yet Another Podcast (https://jesseliberty.com/podcast/

) and is the author of more than two dozen best-selling programming books (https://packt.link/FVtEr

).

Jesse was a Technical Evangelist for Microsoft, Distinguished Software Engineer at AT&T; Software Architect for PBS, and Vice President of Information Technology at Citibank. He was also on the teaching staff at Brandeis University. Jesse has been a Microsoft MVP for 13 years.

Jesse is a recognized expert and has spoken at conferences worldwide. His website is https://jesseliberty.com

.

I have so many people to thank, starting with my co-author, Joe Dluzen, without whom this book would literally have been impossible. I’d also like to thank all the people at Packt, especially Rounak, Prajakta, Kunal, and Vidhisha who stuck in there with us, as well as the technical reviewer. The quality of this book is due to their diligence, though any mistakes are ours. I’d also like to thank my boss for his encouragement and for teaching me so much about creating world-class enterprise APIs. Finally, as ever, I wish to thank my wife, without whose patience and encouragement I could never have written any of my books.

Joseph Dluzen has been working in C# and associated frameworks for almost 20 years. He is currently in a software architecture role for one of the world’s largest agricultural machine manufacturers. Formerly a senior consultant at Accenture, he has experience in a wide range of industries, including government identity, autonomous vehicle tooling, and enterprise auction management systems.

I would like to thank Jesse, without whom this book would never have happened.

About the reviewer

Matheus de Campos , based out of Brazil, is a software engineer with a Bachelor's degree in Computer Science. He has extensive international experience and specializes in Microsoft technologies. Currently, he works as a consultant for tech organizations, focusing on delivering impactful solutions that optimize technology strategies.

Table of Contents

Preface

1

Getting Started

Technical requirements

Where does the API fit in?

The players

Getting set up

Downloading the free software you need

Summary

You try it

2

What We’ll Build

Technical requirements

What is an API and what is it for?

Creating the database

The application

Creating the Car Table

Database structure

Car object

The ASP.NET application

Program.cs

Connecting to the database

Folders

Summary

You try it

3

Implementing with REST

Technical requirements

REST

Client/server

Using web protocols

Statelessness and caching

Implementing REST in ASP.NET Core

DTOs

Dapper

Examining the SQL

Putting it all together (inserting a car)

Creating the body in Postman

Get all

Update

Soft delete

Summary

You try it

4

Documentation with Swagger

Technical requirements

Setting up the Swagger documentation

Swagger for the controller

Swagger out of the box

Running your API in Swagger

param tag

Response codes

Summary

You try it

5

Data Validation

Technical requirements

Tuning your API

Paging

Validation

Capturing errors

Built-in validators

Summary

You try it

6

Azure Functions

Technical requirements

Understanding Functions

Hosting

Application packaging

Billing

Project walkthrough

Starting up

Options

Routing

Deploying

Azure resource creation

Publishing from Visual Studio

Post-deployment reconfiguration

Summary

You try it

7

Azure Durable Functions

Technical requirements

Overview of Durable Functions

Orchestrators

Activities

Programming and debugging walk-through

Additional options

Exceptions

Summary

You try it

8

Advanced Topics

Technical requirements

Implementing an advanced API

Updating the database

Creating the classes

Supporting implementation

Azure Storage Tables

Exploring the essentials

TableModel

StorageTableService

Populating the table in Azure

Introducing Microsoft Aspire

Sample program

Exploring the Aspire dashboard

What have you learned, Dorothy?

Adding Aspire to an existing app

Getting oriented with our new project

Adding Aspire

Summary

You try it

9

Authentication and Authorization

Technical requirements

Introduction to authentication and authorization

Overview of A&A

Enabling authentication on existing functions

Programmatically accessing your API

Authorizing additional Azure Resources

Summary

You try it

10

Deploying to Azure

Technical requirements

Getting started

Using tests to ensure code quality

Using the same binaries

Deploying from DevOps

Importing sample code

Creating the build pipeline

Publishing an artifact

Deploying your artifact to Azure

Continuous deployment

Testing the release pipeline

End-to-end testing

Summary

You try it

Congratulations!

11

What’s Next?

C#

SQL

Database

API architecture

Dapper

AutoMapper

Visual Studio

Git

Housing your version control

Summary

Index

Other Books You May Enjoy

Preface

Building a good Application Program Interface (API) is essential for creating real-world applications that display data from a data source (most often a database). The job of the API, as you’ll see in this book, is the separation of concerns on a large scale; specifically separating the concerns of the frontend from the backend. This allows you to change one (e.g., swap out a new database) without breaking the other (e.g., a website) or vice versa.

A typical enterprise might have multiple teams working on the same overall product. For example, you might have a team working on a web presentation of your data, another working on the iOS version, and a third working on Android.

On the backend, you might have multiple data sources. In the simple example that we use in this book, we examine a car dealership. It might have input from sales, but also from inventory, from a service that provides information on average prices, and so forth. Some of this is static data easily stored in a database, some must be in a frequently updated cache, and some must be obtained on demand.

Coordinating the frontend with the backend is difficult and subject to catastrophic breakage should, for example, the format or calculations in the backend change. Furthermore, the needs of the presentation level are almost guaranteed to change over time. Finally, the frontend is most often not the ideal place to put your business logic.

APIs solve these problems. The frontend talks to well-defined endpoints, and the backend responds with well-defined data. What the backend does to get and manipulate that data is invisible to the frontend. For that matter, the uses that the frontend puts that data to are invisible to the backend. Most importantly, the API itself doesn’t need to know about either; it just knows what is being asked for and how to get it.

Who this book is for

This book is targeted at programmers with at least a working knowledge of C# who want to create world-class APIs, often for enterprise applications. It assumes no prior experience with APIs, though a working acquaintance with SQL will be helpful.

What this book covers

Chapter 1

, Getting Started, provides a quick start to get everything set up locally for development.

Chapter 2

, What We’ll Build, provides an overview of an API in general, and how to use it to decouple a frontend and backend system.

Chapter 3

, Implementing with REST, provides an overview of best practices and an opinionated design for general API development that is used throughout the industry.

Chapter 4

, Documentation with Swagger, shows you how to enable and surface documentation based on Swagger.

Chapter 5

, Data Validation, provides an overview of how to validate API calls, including custom validation with a widely used library.

Chapter 6

, Azure Functions, provides an alternative cloud-first hosting framework that not only can be used for APIs but also as a starting point for much more. It also illustrates best practices and then builds upon them to allow runtime configuration without redeployment.

Chapter 7

, Azure Durable Functions, provides an overview of the simplification that results when following a few small design rules in a stateful, scalable system.

Chapter 8

, Advanced Topics, provides a straightforward, cost-effective, cloud logging implementation. Additionally, it goes over advanced scenarios such as complex object mapping, an opinionated cloud-first design tool, and the creation and use of storage tables.

Chapter 9

, Authentication and Authorization, provides an out-of-the-box solution for cloud-first authentication scenarios, including authorizing Azure and non-Azure clients.

Chapter 10

, Deploying to Azure, gets you set up quickly to iterate with Continuous Delivery and Continuous Integration (CI/CD) pipelines.

Chapter 11

, What’s Next?, gives you practical advice on the classic question: Now what?

To get the most out of this book

You will need a working knowledge of at least the basics of C#. An acquaintance with SQL is helpful but not required. The use of Git and repositories in general will make your life easier. We