Table Of ContentLearning Blazor
Build Single-Page Apps
with WebAssembly and C#
Compliments of
David Pine
Foreword by
Steve Sanderson
Learning Blazor
Take advantage of your C# skills to build UI components and
client-side experiences with .NET. With this practical guide, “The Blazor open
you’ll learn how to use Blazor WebAssembly to develop next- source web framework
generation web experiences. Built on top of ASP.NET Core,
is a whole new way
Blazor represents the future of .NET single-page application
to develop powerful
investments.
applications for the web.
Author David Pine, who focuses on .NET and Azure content Learning Blazor uses
development at Microsoft, explains how WebAssembly tons of examples and
enables many non-JavaScript-based programming languages
prescriptive code based
to run on the client browser. In this book, you’ll learn about
on David Pine’s deep
real-time web functionality with ASP.NET Core SignalR and
experience as a content
discover strategies for bidirectional JavaScript interop. David
developer on the .NET
also covers component data binding, hierarchical event-
team to get you writing
driven communications, in-memory state management, and
Blazor web apps with C#
local storage.
today!”
This book shows you how to:
—Scott Hanselman
• Create a beautiful, feature-rich Blazor app Partner Program Manager,
Developer Division, Microsoft
• Develop and localize an enterprise-scale app using GitHub
Actions and Azure Cognitive Services Translator
• Create advanced validation scenarios for input-based David Pine is a senior content
developer at Microsoft, where he
components with forms
focuses on .NET and Azure developer
• Automatically deploy and host to Azure Static Web Apps, content. He’s recognized as a Google
and rely on HTTP services Developer Expert in Web Technologies
and is a Twilio Champion. Before joining
• Use a geolocation service and speech synthesis and
Microsoft, David was a Microsoft MVP
recognition native to the browser
in Developer Technologies for several
• Author a custom modal verification mechanism for validating years. He thrives in the developer
community, sharing his knowledge
a user
through speaking engagements around
the world.
PROGRAMMING Twitter: @oreillymedia
linkedin.com/company/oreilly-media
US $59.99 CAN $74.99 youtube.com/oreillymedia
IISSBBNN:: 997788--11--049928--0119382441--76
Praise for Learning Blazor
Learning Blazor is the perfect resource for developers who are looking to build modern
web applications using bleeding-edge web technologies. David leverages his skills as a
senior content developer to help you get started with Blazor!
—Scott Hunter, VP Director
Azure Developer Experience, Microsoft
David Pine’s Learning Blazor takes developers on the perfect journey to learning how
to build and deploy their Blazor applications. David leverages his extensive content
development and presentation skills to inspire you to build Blazor web apps today.
—Maria Naggaga, Principal Product Manager Lead, ASP.NET
and .NET Interactive, Microsoft
Like its author, this book will inspire folks to try new things with Blazor and to be excited
about the possibilities of building apps it brings. David’s delightful style of writing code
as eloquent as his prose, coupled with a genuine love for .NET and using it creatively, will
make any developer fall in love with web development all over again.
—Brady Gaster, Principal Program
Manager, .NET Team, Microsoft
As an experienced Blazor developer, I learned more about localization and testing from
David Pine in 20 minutes of reading than I did in days of searching for similar insight
online. Not only is Learning Blazor an educational piece, but it’s also a great reference that
I will return to when building future Blazor applications.
—Jeff Fritz, Live Streamer and Principle Program
Manager, .NET Team, Microsoft
Learning Blazor is a well-paced guide that is perfectly suited for anyone
with .NET experience who would like to learn Blazor to build web apps,
and for anyone looking to refine their Blazor skills.
—Lana Lux, Game Developer, Tech Streamer,
and Founder of Lux Games
Learning Blazor is one of the most informative books I have ever read, and
it makes you want to start developing with WebAssembly and C# right away.
Learning Blazor uses a great storyline and practical real-world examples to explain
a modern technology and how it can be combined with JavaScript and HTML.
A must-read for every web developer.
—Fabian Gosebrink, Senior Developer, Microsoft MVP, and
Google Developer Expert, Offering Solutions Software
There are so many gems in here that you are guaranteed to learn something
regardless of your experience level. It has inspired me to add techniques and
features to my projects that I’ve never considered before.
—Cecil L. Phillip, Staff Developer Advocate, Stripe
Learning Blazor
Build Single-Page Apps
with WebAssembly and C#
David Pine
Foreword by
Steve Sanderson
BBeeiijjiinngg BBoossttoonn FFaarrnnhhaamm SSeebbaassttooppooll TTookkyyoo
Learning Blazor
by David Pine
Copyright © 2023 David Pine. All rights reserved.
Printed in the United States of America.
Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.
O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are
also available for most titles (http://oreilly.com). For more information, contact our corporate/institutional
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Development Editor: Rita Fernando Interior Designer: David Futato
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October 2022: First Edition
Revision History for the First Edition
2022-09-26: First Release
See http://oreilly.com/catalog/errata.csp?isbn=9781098113247 for release details.
The O’Reilly logo is a registered trademark of O’Reilly Media, Inc. Learning Blazor, the cover image, and
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The views expressed in this work are those of the author, and do not represent the publisher’s views.
While the publisher and the author have used good faith efforts to ensure that the information and
instructions contained in this work are accurate, the publisher and the author disclaim all responsibility
for errors or omissions, including without limitation responsibility for damages resulting from the use
of or reliance on this work. Use of the information and instructions contained in this work is at your
own risk. If any code samples or other technology this work contains or describes is subject to open
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This work is part of a collaboration between O’Reilly and Progress Software. See our statement of editorial
independence.
978-1-492-09841-6
[LSI]
Table of Contents
Foreword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
1. Blazing into Blazor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The Origin of Blazor 1
Blazor Hosting 3
Blazor Server 3
Blazor WebAssembly 4
Blazor Hybrid 6
Single-Page Applications, Redefined 6
Why Adopt Blazor 7
.NET’s Potential in the Browser 8
.NET Is Here to Stay 9
Familiarity 9
Safe and Secure 10
Code Reuse 10
Tooling 11
Open Source Software 13
Your First Blazor App with the .NET CLI 14
Build the App 15
Install Dev-cert 15
Run the App 16
The Code Must Live On 17
Perusing the “Learning Blazor” Sample App 19
Summary 21
iii
2. Executing the App. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Requesting the Initial Page 24
App Startup and Bootstrapping 25
Blazor WebAssembly App Internals 32
Detecting Client Culture at Startup 34
Layouts, Shared Components, and Navigation 35
Summary 59
3. Componentizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Design with the User in Mind 61
Leveraging “Pwned” Functionality 63
“Have I Been Pwned” Client Services 65
Restricting Access to Resources 73
The Introduction Component Says “Hi” 75
The Joke Component and Services 77
Aggregating Joke Services—Laughter Ensues 81
DI from Library Authors 88
Forecasting Local Weather 89
Summary 103
4. Customizing the User Login Experience. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
A Bit More on Blazor Authentication 105
Client-Side Custom Authorization Message Handler Implementation 106
The Web.Client ConfigureServices Functionality 113
Native Speech Synthesis 117
Sharing and Consuming Custom Components 123
Chrome: The Overloaded Term 124
Modal Modularity and Blazor Component Hierarchies 124
Exploring Blazor Event Binding 129
Summary 137
5. Localizing the App. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
What Is Localization? 139
The Localization Process 140
The Language Selection Component 143
Automating Translations with GitHub Actions 151
Localization in Action 154
Summary 165
6. Exemplifying Real-Time Web Functionality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Defining the Server-Side Events 167
iv | Table of Contents
Exposing Twitter Streams and Chat Functionality 168
Writing Contextual RPC and Inner-Process Communication 174
Configuring the Hub Endpoint 177
Consuming Real-Time Data on the Client 181
Configuring the Client 181
Sharing a Hub Connection 182
Consuming Real-Time Data in Components 190
Summary 204
7. Using Source Generators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
What Are Source Generators? 205
Building a Case for Source Generators 206
C# Source Generators in Action 209
Source Generating the localStorage API 209
Source Generating the Geolocation API 215
Example Usage of the ILocalStorageService 223
Summary 231
8. Accepting Form Input with Validation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
The Basics of Form Submission 233
Framework-Provided Components for Forms 234
Models and Data Annotations 235
Defining Component Models 236
Defining and Consuming Validation Attributes 237
Implementing a Contact Form 240
Implementing Speech Recognition as User Input 252
Reactive Programming with the Observer Pattern 259
Managing Callbacks with a Registry 261
Applying the Speech Recognition Service to Components 263
Form Submission Validation and Verification 266
Summary 268
9. Testing All the Things. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
Why Test? 269
Unit Testing 269
Defining Unit-Testable Code 270
Writing an Extension Method Unit Test 272
Component Testing 276
End-to-End Testing with Playwright 279
Automating Test Execution 284
Summary 286
Table of Contents | v
