The C# Workshop: Kickstart your career as a software developer with C#

Cover....1

FM....2

Copyright....3

Table of Contents....4

Preface....20

Chapter 1: Hello C#....68

Introduction....69

Running and Developing C# with the .NET CLI....69

Creating Programs with the CLI and VS Code....71

Basic Anatomy of a C# Program....72

Exercise 1.01: Creating a Console App that Says "Hello World"....72

Top-Level Statements....73

Declaring Variables....74

Declaring Variables Explicitly....75

Declaring Variables Implicitly....76

Explicit versus Implicit Declaration....76

Exercise 1.02: Assigning Variables to User Inputs....77

Data Types....78

Strings....78

Exercise 1.03: Checking String Immutability....79

Comparing Strings....80

Numeric Types....81

Exercise 1.04: Using the Basic Arithmetic Operators....82

Classes....83

Dates....86

Exercise 1.05: Using Date Arithmetic.....87

Formatting Dates....89

Logical Operators and Boolean Expressions....89

Using if-else Statements....91

Exercise 1.06: Branching with if-else....91

The Ternary Operator....94

Reference and Value Types....94

Exercise 1.07: Grasping Value and Reference Equality ....97

Default Value Types....100

Enhancing Decision Making with the switch Statement....100

Exercise 1.08: Using switch to Order Food....101

Iteration Statements....104

while....104

Exercise 1.09: Checking Whether a Number is Prime with a while Loop....105

Jump Statements....106

do-while....109

Arrays....109

for Loops....110

Exercise 1.10: Ordering an Array Using Bubble Sort....111

foreach Statements....113

File Handling....114

FileAccess....115

FileMode....115

Exercise 1.11: Reading Content from Text Files....116

Disposable Objects....117

Exercise 1.12: Writing to a Text File....118

Exceptions....120

Exercise 1.13: Handling Invalid User Inputs with try/catch....120

Activity 1.01: Creating a Guessing Game....124

Summary....125

Chapter 2: Building Quality Object-Oriented Code....128

Introduction....129

Classes and Objects....129

Constructors....130

Fields and Class Members....131

Exercise 2.01: Creating Classes and Objects....132

Reference Types....134

Properties....138

Object Initialization....142

Comparing Functions and Methods....143

An Effective Class....144

Exercise 2.02: Comparing the Area Occupied by Different Shapes....146

The Four Pillars of OOP....151

Encapsulation....151

Inheritance....152

Polymorphism....159

What is the Benefit of Polymorphism?....161

Abstraction....164

Interfaces....168

Exercise 2.03: Covering Floor in the Backyard....172

SOLID Principles in OOP....175

Single Responsibility Principle....176

Open-Closed Principle....180

Liskov Substitution....181

Interface Segregation....182

Dependency Inversion....185

How C# Helps with Object-Oriented Design....188

Static....189

Sealed....191

Partial....191

Virtual....192

Internal....193

Conditional Operators....193

Ternary Operators....194

Overloading Operators....196

Nullable Primitive Types....198

Generics....199

Enum....203

Extension Methods....203

Struct....204

Record....207

Init-Only Setters....211

ValueTuple and Deconstruction....211

Exercise 2.04: Creating a Composable Temperature Unit Converter....213

Activity 2.01: Merging Two Circles....220

Summary....222

Chapter 3: Delegates, Events, and Lambdas....224

Introduction....225

Delegates....226

Defining a Custom Delegate....232

Exercise 3.01: Defining and Invoking Custom Delegates....233

The Inbuilt Action and Func Delegates....238

Assigning Delegates....241

Invoking a Delegate....243

Exercise 3.02: Assigning and Invoking Delegates....244

Multicast Delegates....250

Exercise 3.03: Invoking a Multicast Delegate....252

Multicasting with a Func Delegate....258

What Happens When Things Go Wrong?....260

Exercise 3.04: Ensuring All Target Methods Are Invoked in a Multicast Delegate....261

Events....266

Defining an Event....266

Exercise 3.05: Publishing and Subscribing to Events....271

Events or Delegates?....275

Static Events Can Cause Memory Leaks....276

Lambda Expressions....277

Exercise 3.06: Using a Statement Lambda to Reverse Words in a Sentence....281

Captures and Closures....283

Activity 3.01: Creating a Web File Downloader....287

Summary....290

Chapter 4: Data Structures and LINQ....292

Introduction....293

Data Structures....293

Lists....297

Exercise 4.01: Maintaining Order within a List....305

Queues....310

Stacks....312

HashSets....317

Dictionaries....319

Exercise 4.02: Using a Dictionary to Count the Words in a Sentence....324

LINQ....328

Query Operators....329

Query Expressions....330

Deferred Execution....330

Standard Query Operators....331

Projection Operations....331

Select....331

Anonymous Types....332

SelectMany....335

Filtering Operations....337

Sorting Operations....343

OrderBy and OrderByDescending....343

ThenBy and ThenByDescending....345

Exercise 4.03: Filtering a List of Countries by Continent and Sorting by Area....348

Partitioning Operations....350

Grouping Operations....353

Exercise 4.04: Finding the Most Commonly Used Words in a Book....355

Aggregation Operations....361

Quantifier Operations....364

Join Operations....368

Using a let Clause in Query Expressions....371

Activity 4.01: Treasury Flight Data Analysis....372

Summary....378

Chapter 5: Concurrency: Multithreading Parallel and Async Code....380

Introduction....381

Running Asynchronous Code Using Tasks....384

Creating a New Task....384

Using Task.Factory.StartNew....389

Using Task.Run....390

Exercise 5.01: Using Tasks to Perform Multiple Slow-Running Calculations....393

Coordinating Tasks....396

Waiting for Tasks to Complete....397

Exercise 5.02: Waiting for Multiple Tasks to Complete Within a Time Period....399

Continuation Tasks....403

Using Task.WhenAll and Task.WhenAny with Multiple Tasks....406

Exercise 5.03: Waiting for All Tasks to Complete....407

Asynchronous Programming....415

Async Lambda Expressions....422

Canceling Tasks....425

Exercise 5.04: Canceling Long-Running Tasks....427

Exception Handling in Async/Await Code....436

Exercise 5.05: Handling Async Exceptions....439

The AggregateException Class....443

IAsyncEnumerable Streams....448

Parallel Programming....451

Data Parallelism....452

Task Parallelism....452

The Parallel Class....453

Parallel.For and Parallel.ForEach....455

Activity 5.01: Creating Images from a Fibonacci Sequence....468

Summary....474

Chapter 6: Entity Framework with SQL Server....476

Introduction....477

Creating a Demo Database Before You Start....478

Modeling Databases Using EF....479

Connection String and Security....481

Which One to Choose—EF or EF Core?....484

Model....485

DbContext and DbSet....488

AdventureWorks Database....492

Exercise 6.01: Reading Stock Locations from AdventureWorks Database....492

Querying a Database—LINQ to SQL....495

Query Syntax....497

The Rest of CRUD....499

Exercise 6.02: Updating Products and Manufacturers Table....503

Database First....507

Revisiting DbContext....509

Generating DbContext from an Existing Database....511

Code First and Migrations....512

Exercise 6.03: Managing Product Price Changes....516

Pitfalls of EF....520

Examples Setup....521

Multiple Adds....523

Equals over ==....524

Using IEnumerable over IQueryable....525

Lazy over Eager Loading....526

Read-Only Queries....527

Summary of Results....527

Tools to Help You Spot Problems Early On....528

Working with a Database in Enterprise....529

Repository Pattern....529

Exercise 6.04: Creating a Generic Repository....532

Testing Data Persistence Logic Locally....536

In-Memory Database Provider....536

SQLite Database Provider....538

A Few Words on Repository....540

Query and Command Handlers Patterns....541

Separating the Database Model from the Business Logic (Domain) Model....544

Activity 6.01: Tracking System for Trucks Dispatched....545

Summary....547

Chapter 7: Creating Modern Web Applications with ASP.NET....550

Introduction....551

Anatomy of an ASP.NET Web App....551

Program.cs and the WebApplication....553

Middlewares....554

Logging....555

Dependency Injection....557

Exercise 7.01: Creating Custom Logging Middleware....558

Dependency Lifetimes....563

Razor Pages....565

Basic Razor Syntax....565

File Structure....566

Exercise 7.02: Creating a Kanban Board with Razor....568

PageModel....571

The Life Cycle with Page Handlers....572

Rendering Reusable Static Code with Tag Helpers....573

Exercise 7.03: Creating Reusable Components with Tag Helpers....574

Model Binding....579

Exercise 7.04: Creating a New Page to Submit Tasks....579

Validation....586

Dynamic Behavior with Partial Pages....587

Exercise 7.05: Refactoring a Tag Helper to a Partial Page with Custom Logic....588

Activity 7.01: Creating a Page to Edit an Existing Task....590

View Components....591

Exercise 7.06: Creating a View Component to Display Task Statistics....593

Activity 7.02: Writing a View Component to Display Task Log....597

Summary....599

Chapter 8: Creating and Using Web API Clients....602

Introduction....603

Browser....604

Web API....606

RESTful API....606

Postman....607

Client....609

Octokit....609

API Key....611

Azure Text Analytics....611

Exercise 8.01: Performing Sentimental Text Analysis on Any Text....616

Your Own Client....621

HttpClient....621

HttpClient and IDisposable....625

OAuth....626

Real-life Analogy....626

API Analogy....626

OAuth App for GitHub....626

Authorization Header....632

Basic Authentication....634

API Key and Personal Access Token....635

Third-Party Authentication—OAuth2....637

Request Idempotency....643

PUT, PATCH, or POST....643

Exercise 8.02: HttpClient Calling a Star Wars Web API....643

Activity 8.01: Reusing HttpClient for the Rapid Creation of API Clients....648

RestSharp....650

Activity 8.02: The Countries API Using RestSharp to List all Countries....652

Refit....653

Activity 8.03: The Countries API Using Refit to List all Countries....654

Other Ways of Making HTTP Requests....655

Exercise 8.03: A Strongly Typed HTTP Client for Testing Payments in a PayPal Sandbox....656

Activity 8.04: Using an Azure Blob Storage Client to Upload and Download Files....667

Summary....670

Chapter 9: Creating API Services....672

Introduction....673

ASP.NET Core Web API....673

Creating a New Project....673

Web API Project Structure....675

An In-Depth Look at WeatherForecastController....675

Responding with Different Status Codes....677

Exercise 9.01: .NET Core Current Time Service....681

Bootstrapping a Web API....682

Dependency Injection....682

Program.cs and Minimal API....682

The Inner Workings of the AddLogging Method....685

The Lifetime of an Injected Component....685

DI Examples within a Service....686

Singleton....690

Scoped....691

Transient....691

TryAdd....692

Manual Injection Using an IoC Container....693

Exercise 9.02: Displaying Current Time in a Country API Time Zone....695

OpenAPI and Swagger....697

Using Swagger Swashbuckle....697

Error Handling....709

Request Validation....710

Configuration....713

Development Environments and Configuration....714

Bootstrapping....716

Calling Another API....721

RapidAPI....721

Service Client....728

DTO and Mapping Using AutoMapper....730

HttpClient DI....732

Exercise 9.03: Performing File Operations by Calling Azure Blob Storage....734

Securing a Web API....745

Azure Active Directory....745

JWT....746

OpenID Connect....746

Application Registration....747

Implementing Web API Security....750

Token Generator App....751

Configuring Swagger Auth....757

Troubleshooting Token Validation Errors....760

Service-Oriented Architecture....761

Microservice Architecture....762

Activity 9.01: Implementing the File Upload Service Using Microservice Architecture....762

Azure Functions....765

Summary....770

Index....774

C# is a powerful, versatile language that can unlock a variety of career paths. But, as with any programming language, learning C# can be a challenging process. With a wide range of different resources available, it's difficult to know where to start.

That's where The C# Workshop comes in. Written and reviewed by industry experts, it provides a fast-paced, supportive learning experience that will quickly get you writing C# code and building applications. Unlike other software development books that focus on dry, technical explanations of the underlying theory, this Workshop cuts through the noise and uses engaging examples to help you understand how each concept is applied in the real world.

As you work through the book, you'll tackle realistic exercises that simulate the type of problems that software developers work on every day. These mini-projects include building a random-number guessing game, using the publisher-subscriber model to design a web file downloader, creating a to-do list using Razor Pages, generating images from the Fibonacci sequence using async/await tasks, and developing a temperature unit conversion app which you will then deploy to a production server.

 By the end of this book, you'll have the knowledge, skills, and confidence to advance your career and tackle your own ambitious projects with C#.

What You Will Learn:

• Understand the fundamentals of programming with C# 10 and .NET 6
• Build your familiarity with .NET CLI and Visual Studio Code
• Master the fundamentals of object-oriented programming (OOP)
• Understand and implement concurrency to write more efficient code
• Create a database and handle data using C#, SQL, and Entity Framework
• Build web applications using the ASP.NET framework
• Run automated unit tests with NUnit to validate your code
• Use principles including SOLID, KISS, ACID, DRY, and design patterns

Who this book is for:

This book is for aspiring C# developers. It is recommended that you already have a basic understanding of core programming concepts before you start. Prior experience of another programming language would be beneficial, though it is not absolutely necessary.