Code like a Pro in C#

Code Like a Pro in C#....1

contents....5

preface....11

acknowledgments....13

about this book....15

Who should read this book....15

How this book is organized: A roadmap....16

About the code....17

liveBook discussion forum....18

about the author....19

about the cover illustration....20

Part 1—Using C# and .NET....21

1 Introducing C# and .NET....23

1.1 Why work in C#?....25

1.1.1 Reason 1: C# is economical....26

1.1.2 Reason 2: C# is maintainable....26

1.1.3 Reason 3: C# is developer friendly and easy to use....27

1.2 Why not work in C#?....27

1.2.1 Operating system development....28

1.2.2 Real-time operating system embedded development in C#....28

1.2.3 Numerical computing and C#....29

1.3 Switching to C#....29

1.4 What you will learn in this book....32

1.5 What you will not learn in this book....32

Summary....34

2 .NET and how it compiles....35

2.1 What is the .NET Framework?....36

2.2 What is .NET 5?....37

2.3 How CLI-compliant languages are compiled....39

2.3.1 Step 1: C# code (high-level)....40

2.3.2 Step 2: Common Intermediate Language (assembly level)....43

2.3.3 Step 3: Native code (processor level)....49

Exercises....51

Summary....52

Part 2—The existing codebase....53

3 How bad is this code?....55

3.1 Introducing Flying Dutchman Airlines....56

3.2 Pieces of the puzzle: Taking a look at our requirements....58

3.2.1 Object-relational mapping....58

3.2.2 The GET /flight endpoint: Retrieving information on all flights....59

3.2.3 The GET /flight/{flightNumber} endpoint: Getting specific flight information....60

3.2.4 The POST /booking/{flightNumber} endpoint: Booking a flight....61

3.3 Coming to terms with the existing codebase....63

3.3.1 Assessing the existing database schema and its tables....63

3.3.2 The existing codebase: Web service configuration files....64

3.3.3 Considering models and views in the existing codebase....70

Summary....77

4 Manage your unmanaged resources!....78

4.1 The FlightController: Assessing the GET /flight endpoint....80

4.1.1 The GET /flight endpoint and what it does....80

4.1.2 Method signature: The meaning of ResponseType and typeof....81

4.1.3 Collecting flight information with collections....83

4.1.4 Connection strings, or how to give a security engineer a heart attack....84

4.1.5 Using IDisposable to release unmanaged resources....85

4.1.6 Querying a database with SqlCommand....87

4.2 The FlightController: Assessing GET /flight/{flightNumber}....90

4.3 The FlightController: POST /flight....93

4.4 The FlightController: DELETE /flight/{flightNumber}....97

Exercises....98

Summary....99

Part 3—The database access layer....101

5 Setting up a project and database with Entity Framework Core....103

5.1 Creating a .NET 5 solution and project....104

5.2 Setting up and configuring a web service....108

5.2.1 Configuring a .NET 5 web service....109

5.2.2 Creating and using HostBuilder....111

5.2.3 Implementing the Startup class....113

5.2.4 Using the repository/service pattern for our web service architecture....116

5.3 Implementing the database access layer....118

5.3.1 Entity Framework Core and reverse-engineering....118

5.3.2 DbSet and the Entity Framework Core workflow....120

5.3.3 Configuration methods and environment variables....122

5.3.4 Setting an environment variable on Windows....123

5.3.5 Setting an environment variable on macOS....124

5.3.6 Retrieving environment variables at run time in your code....124

Exercises....127

Summary....127

Part 4—The repository layer....129

6 Test-driven development and dependency injection....131

6.1 Test-driven development....133

6.2 The CreateCustomer method....137

6.2.1 Why you should always validate input arguments....138

6.2.2 Using “arrange, act, assert” to write unit tests....139

6.2.3 Validating against invalid characters....140

6.2.4 In-lining test data with the [DataRow] attribute....143

6.2.5 Object initializers and autogenerated code....143

6.2.6 Constructors, reflection, and asynchronous programming....145

6.2.7 Locks, mutexes, and semaphores....147

6.2.8 Synchronous to asynchronous execution . . . continued....149

6.2.9 Testing Entity Framework Core....150

6.2.10 Controlling dependencies with dependency injection....152

Summary....159

7 Comparing objects....160

7.1 The GetCustomerByName method....161

7.1.1 Question marks: Nullable types and their applications....163

7.1.2 Custom exceptions, LINQ, and extension methods....164

7.2 Congruence: From the Middle Ages to C#....169

7.2.1 Creating a “comparer” class using EqualityComparer....170

7.2.2 Testing equality by overriding the Equals method....173

7.2.3 Overloading the equality operator....174

Exercises....177

Summary....178

8 Stubbing, generics, and coupling....180

8.1 Implementing the Booking repository....181

8.2 Input validation, separation of concerns, and coupling....184

8.3 Using object initializers....189

8.4 Unit testing with stubs....192

8.5 Programming with generics....196

8.6 Providing default arguments by using optional parameters....197

8.7 Conditionals, Func, switches, and switch expressions....199

8.7.1 The ternary conditional operator....200

8.7.2 Branching using an array of functions....201

8.7.3 Switch statements and expressions....201

8.7.4 Querying for pending changes in Entity Framework Core....203

Exercises....205

Summary....206

9 Extension methods, streams, and abstract classes....208

9.1 Implementing the Airport repository....209

9.2 Getting an Airport out of the database by its ID....210

9.3 Validating the AirportID input parameter....212

9.4 Output streams and being specifically abstract....214

9.5 Querying the database for an Airport object....219

9.6 Implementing the Flight repository....226

9.6.1 The IsPositive extension method and “magic numbers”....228

9.6.2 Getting a flight out of the database....234

Exercises....236

Summary....237

Part 5—The service layer....239

10 Reflection and mocks....241

10.1 The repository/service pattern revisited....242

10.1.1 What is the use of a service class?....243

10.2 Implementing the CustomerService....245

10.2.1 Setting up for success: Creating skeleton classes....245

10.2.2 How to delete your own code....247

10.3 Implementing the BookingService....249

10.3.1 Unit testing across architectural layers....254

10.3.2 The difference between a stub and a mock....255

10.3.3 Mocking a class with the Moq library....256

10.3.4 Calling a repository from a service....263

Exercises....265

Summary....266

11 Runtime type checking revisited and error handling....268

11.1 Validating input parameters of a service layer method....269

11.1.1 Runtime type checks with the is and as operators....273

11.1.2 Type checking with the is operator....273

11.1.3 Type checking with the as operator....275

11.1.4 What did we do in section 11.1?....275

11.2 Cleaning up the BookingServiceTests class....276

11.3 Foreign key constraints in service classes....278

11.3.1 Calling the Flight repository from a service class....279

Exercises....290

Summary....292

12 Using IAsyncEnumerable and yield return....293

12.1 Do we need an AirportService class?....294

12.2 Implementing the FlightService class....296

12.2.1 Getting information on a specific flight from the FlightRepository....296

12.2.2 Combining two data streams into a view....300

12.2.3 Using the yield return keywords with try-catch code blocks....308

12.2.4 Implementing GetFlightByFlightNumber....312

Exercises....318

Summary....319

Part 6—The controller layer....321

13 Middleware, HTTP routing, and HTTP responses....323

13.1 The controller class within the repository/service pattern....324

13.2 Determining what controllers to implement....326

13.3 Implementing the FlightController....328

13.3.1 Returning HTTP responses with the IActionResult interface (GetFlights)....329

13.3.2 Injecting dependencies into a controller using middleware....332

13.3.3 Implementing the GET /Flight/{FlightNumber} endpoint....340

13.4 Routing HTTP requests to controllers and methods....344

Exercises....350

Summary....350

14 JSON serialization/ deserialization and custom model binding....352

14.1 Implementing the BookingController class....353

14.1.1 Introduction to data deserialization....355

14.1.2 Using the [FromBody] attribute to deserialize incoming HTTP data....359

14.1.3 Using a custom model binder and method attribute for model binding....360

14.1.4 Implementing the CreateBooking endpoint method logic....363

14.2 Acceptance testing and Swagger middleware....369

14.2.1 Manual acceptance testing with an OpenAPI specification....369

14.2.2 Generating an OpenAPI specification at runtime....374

14.3 The end of the road....380

Summary....381

Appendix A—Exercise answers....383

Chapter 2: .NET and how it compiles....383

Chapter 4: Manage your unmanaged resources!....384

Chapter 5: Setting up a project and database with Entity Framework Core....384

Chapter 6: Test-driven development and dependency injection....385

Chapter 7: Comparing objects....386

Chapter 8: Stubbing, generics, and coupling....387

Chapter 9: Extension methods, streams, and abstract classes....387

Chapter 10: Reflection and mocks....388

Chapter 11: Runtime type checking revisited and error handling....389

Chapter 12: Using IAsyncEnumerable and yield return....389

Chapter 13: Middleware, HTTP routing, and HTTP responses....390

Appendix B—Clean code checklist....391

Appendix C—Installation guides....393

Appendix D—OpenAPI FlyTomorrow....397

Appendix E—Reading list....400

index....405

Symbols....405

A....405

B....406

C....406

D....407

E....408

F....408

G....409

H....409

I....410

J....410

K....411

L....411

M....411

N....412

O....412

P....412

Q....413

R....413

S....414

T....415

U....415

V....416

W....416

Y....416

Code Like a Pro in C# teaches you to how write clean C# code that’s suitable for enterprise applications. In this book, you’ll refactor a legacy codebase by applying modern C# techniques. You’ll explore tools like Entity Framework Core, design techniques like dependency injection, and key practices like testing and clean coding. It’s a perfect path to upgrade your existing C# skills or shift from another OO language into C# and the .NET ecosystem.

What's inside

• Unit testing and test-driven development
• Refactor a legacy .NET codebase
• Principles of clean code
• Query and manipulate databases with LINQ and Entity Framework Core

About the reader

For developers experienced with object-oriented programming. No C# experience required.