Head First C#: A Learner's Guide to Real-World Programming with C# and .NET. 5 Ed

Title page....6

Copyright....8

About the authors....10

Table of Contents....10

Introduction....31

Who is this book for?....32

We know what you’re thinking....33

We know what your brain is thinking....33

Metacognition: thinking about thinking....35

Here’s what WE did....36

README.md....38

The technical review team....40

Acknowledgments....42

Chapter 1....43

Learn C#…and learn to become a great developer....44

Write code and explore C# with Visual Studio ....45

Install Visual Studio Community Edition....46

Run Visual Studio....47

Create and run your first C# project in Visual Studio....48

You can use Visual Studio Code with Head First C#....54

Install the C# extensions....55

Create and run your first project in Visual Studio Code....56

Set up Visual Studio Code for the next project....59

Let’s build a game!....60

Break up large projects into smaller parts....62

Here’s how you’ll build your game....63

Create a .NET MAUI project in Visual Studio....64

Run your new .NET MAUI app....66

MAUI apps work on all of your devices....67

Here’s the page that you’ll build....68

Start editing your XAML code....69

Add the XAML for a Button and a Label....70

Use a FlexLayout to make a grid of animal buttons....76

Write C# code to add the animals to the buttons....80

Start editing the PlayAgainButton event handler method....81

Add more statements to your event handler....82

Add animals to your buttons....84

Run your app! ....88

Visual Studio makes it easy to use Git....93

Add C# code to handle mouse clicks....94

Enter the code for the event handler....97

Run your app and find all the pairs....98

Finish the game by adding a timer....101

Add a timer to your game’s code....102

Finish the code for your game....104

Even better ifs…....106

Chapter 2....107

Take a closer look at the files in your console app....108

Statements are the building blocks for your apps....110

Statements live inside methods....111

Your methods use variables to work with data....112

Generate a new method to work with variables....114

Add code that uses operators to your method....115

Use the debugger to watch your variables change....116

Use code snippets to help write loops....118

Use operators to work with variables....119

if statements make decisions....120

Loops perform an action over and over....121

Controls drive the mechanics of your user interfaces....130

Other controls you’ll use in this book....131

Build a .NET MAUI app to experiment with controls....132

Create a new app to experiment with controls....133

Explore your new MAUI app and figure out how it works....134

Add an Entry control to your app....138

Add properties to your Entry control....139

Make your Entry control update a Label control....140

Combine horizontal and vertical stack layouts....145

Add a Picker control to display a list of choices....146

Unity Lab #1....153

Unity is a powerful tool for game design....154

Download Unity Hub....155

Use Unity Hub to create a new project....156

Your scene is a 3D environment....158

Unity games are made with GameObjects....159

Use the Move Gizmo to move your GameObjects....160

The Inspector shows your GameObject’s components....161

Add a material to your Sphere GameObject....162

Rotate your sphere....165

Get creative!....168

Chapter 3....169

Classes help you organize your code....170

If code is useful, classes can help you reuse it....171

Some methods take parameters and return a value....172

Visual Studio helps you explore parameters and return values....173

Let’s build an app that picks random cards....174

You’ll use an array to store the cards....175

Create an app with a Main method....176

Add a class called CardPicker to your app....178

Use Quick Actions to remove unnecessary using lines....180

Convert between namespace styles....181

Use the new keyword to create an array of strings....182

Ana’s working on her next game....187

Ana’s game is evolving…....188

Build a paper prototype for a classic game....190

Build a MAUI version of your random card app....192

Make your MAUI app pick random cards....195

Reuse your CardPicker class....196

Add a using directive to use code in another namespace....197

Ana's prototypes look great…....199

Ana can use objects to solve her problem....200

You use a class to build an object....201

When you create a new object from a class, it’s called an instance of that class....202

A better solution for Ana…brought to you by objects....203

An instance uses fields to keep track of things....207

Thanks for the memory....210

What’s on your app’s mind....211

Sometimes code can be difficult to read....212

Most code doesn’t come with a manual....213

Use intuitive class and method names....214

Build a class to work with some guys....220

There’s an easier way to initialize objects with C# ....222

Use the C# Interactive window or csi to run C# code....230

Chapter 4....231

Owen could use our help!....232

Character sheets store different types of data on paper....233

A variable’s type determines what kind of data it can store....234

C# has several types for storing integers....235

Types for storing really HUGE and really numbers....236

Let’s talk about strings....237

A literal is a value written directly into your code....238

A variable is like a data to-go cup....241

Other types come in different sizes too....242

10 pounds of data in a 5-pound bag....243

Casting lets you copy values that C# can’t automatically convert to another type....244

C# does some conversions automatically....247

When you call a method, the arguments need to be compatible with the types of the parameters....248

Owen is constantly improving his game…....250

Let’s help Owen experiment with ability scores....252

Fix the compiler error by adding a cast....254

Use reference variables to access your objects....264

References are like sticky notes for your objects....265

If there aren’t any more references,your object gets garbage-collected....266

Multiple references and their side effects....268

Two references mean TWO variables that can change the same object’s data....275

Objects use references to talk to each other....276

Arrays hold multiple values....278

Arrays can contain reference variables....279

null means a reference points to nothing....283

Use the string? type when a string might be null....285

Welcome to Sloppy Joe’s Budget House o’ Discount Sandwiches!....288

Sloppy Joe's menu app uses a Grid layout....289

Grid controls ....290

Define the rows and columns for a Grid....291

Create the Sloppy Joe's menu app and set up the grid....292

The C# code for the main page....294

Can we make the app more accessible? ....297

Use the SetValue method to change a control’s semantic properties....298

Unity Lab #2....299

C# scripts add behavior to your GameObjects....300

Add a C# script to your GameObject....301

Write C# code to rotate your sphere....302

Add a breakpoint and debug your game....304

Use the debugger to understand Time.deltaTime....305

Add a cylinder to show where the Y axis is....306

Add fields to your class for the rotation angle and speed....307

Use Debug.DrawRay to explore how 3D vectors work....308

Run the game to see the ray in the Scene view....309

Rotate your ball around a point in the scene....310

Use Unity to take a closer look at rotation and vectors....311

Get creative!....312

Chapter 5....313

Let’s help Owen roll for damage....314

Create a console app to calculate damage....315

Design a MAUI version of the damage calculator app....317

Tabletop talk (or maybe…dice discussion?)....321

Let’s try to fix that bug....322

Use Debug.WriteLine to print diagnostic information....323

It’s easy to accidentally misuse your objects....326

Encapsulation means keeping some data in a class private....327

Use encapsulation to control access to your class’s methods and fields....328

But is the RealName field REALLY protected?....329

Private fields and methods can only be accessed from instances of the same class....330

Why encapsulation? Think of an object as an opaque box…....335

Let’s use encapsulation toimprove the SwordDamage class....339

Encapsulation keeps your data safe....340

Write a console app to test the PaintballGun class....341

Properties make encapsulation easier....342

Modify your top-level statements to use the Balls property....343

Auto-implemented properties simplify your code....344

Use a private setter to create a read-only property....345

What if we want to change the magazine size?....346

Use a constructor with parameters to initialize properties....347

Specify arguments when you use the new keyword....348

Initialize fields and properties inline or in the constructor....355

Make the screen reader announce each roll....363

A few useful facts about methods and properties....364

Chapter 6....367

Calculate damage for MORE weapons....368

Use a switch statement to match several candidates....369

One more thing…can we calculate damage for a dagger? And a mace? And a staff? and.......371

When your classes use inheritance, you only need to write your code once....372

Build up your class model by starting general and getting more specific....373

How would you design a zoo simulator?....374

Different animals have different behaviors....376

Every subclass extends its base class....379

Any place where you can use a base class, you can use one of its subclasses instead....380

Use a colon to extend a base class....384

We know that inheritance adds the base class fields, properties, and methods to the subclass…....385

A subclass can override methods to change or replace members it inherited....386

Some members are only implemented in a subclass....391

Use the debugger to understand how overriding works....392

Build an app to explore virtual and override....394

A subclass can hide methods in the base class....396

Use the override and virtual keywords to inherit behavior....398

A subclass can access its base class using the base keyword....400

When a base class has a constructor, your subclass needs to call it....401

A subclass and base class can have different constructors....402

It’s time to finish the job for Owen....403

A class should do one thing....408

Build a beehive management system....412

How the Beehive Management System app works....413

The page uses a grid to lay out the controls for the UI....414

The Beehive Management System class model....417

All bees in the system extend the Bee class....418

All the constants are in their own static class....419

The worker bees extend the Bee class....420

The Queen class: how she manages the worker bees....423

Here’s the code-behind for MainPage.xaml.cs....424

Feedback drives your beehive management game....430

The Beehive Management System is turn-based…now let’s convert it to real-time....432

Some classes should never be instantiated....434

An abstract class is an intentionally incomplete class....436

Like we said, some classes should never be instantiated....438

An abstract method doesn’t have a body....439

Abstract properties work just like abstract methods....440

The Deadly Diamond of Death....443

Unity Lab #3....445

Let’s build a game in Unity!....446

Create a new material inside the Materials folder....447

Spawn a billiard ball at a random point in the scene....448

Use the debugger to understand Random.value....449

Turn your GameObject into a prefab....450

Create a script to control the game....451

Attach the GameController script to the Main Camera....452

Press Play to run your code....453

Use the Inspector to work with GameObject instances ....454

Use physics to keep balls from overlapping....455

Get creative!....456

Chapter 7....457

The beehive is under attack!....458

We could use casting to call the DefendHive method…....459

An interface defines methods and properties that a class must implement…....460

Interfaces let unrelated classes do the same job....461

Get a little practice using interfaces....462

If you’re given… What’s the picture?....464

If you’re given… What’s the declaration?....465

You can’t instantiate an interface, but you can reference an interface....468

Interface references are ordinary object references....471

The RoboBee 4000 can do a worker bee’s job without using valuable honey....472

The IWorker's Job property is a hack....476

Use is to check the type of an object....477

Use is to access methods in a subclass....478

What if we want different animals to swim or hunt in packs?....480

Use interfaces to work with classes that do the same job....481

Safely navigate your class hierarchy with is....482

C# has another tool for safe type conversion: the as keyword....483

Use upcasting and downcasting tomove up and down a class hierarchy....484

A quick example of upcasting ....485

Upcasting turns your CoffeeMaker into an Appliance....486

Downcasting turns your Appliance back into a CoffeeMaker....487

Upcasting and downcasting work with interfaces too....488

Interfaces can inherit from other interfaces....490

Interfaces can have static members....497

Default implementations give bodies to interface methods....498

Add a ScareAdults method with a default implementation....499

Data binding updates MAUI controls automatically....501

Add data binding to the default MAUI app....502

Make Moods implement the INotifyPropertyChanged interface....504

Use the PropertyChanged event to make data binding work....505

Polymorphism means that one object can take many different forms....511

Chapter 8....515

If a constructor just sets fields, use a primary constructor instead....516

A primary constructor can extend a base constructor....517

Strings don’t always work for storing categories of data....518

Enums let you work with a set of valid values....519

Enums let you represent numbers with names ....520

We could use an array to create a deck of cards…....523

Arrays can be annoying to work with....524

Lists make it easy to store collections of…anything....525

Lists are more flexible than arrays....526

Let’s build an app to store shoes....529

Generic collections can store any type....532

You can use collection expressions to create Lists....538

Let’s create a List of Ducks....539

Sorting lists can be tricky....540

IComparable helps your List sort its Ducks....541

Use IComparer to tell your List how to sort....542

Create an instance of your comparer object....543

Comparers can do complex comparisons....544

Overriding a ToString method lets an object describe itself ....547

Update your foreach loops to let your Ducks and Cards write themselves to the console....548

You can upcast an entire list using IEnumerable....552

Use a Dictionary to store keys and values....554

The Dictionary functionality rundown....555

Write an app that uses a Dictionary ....557

And yet MORE collection types… ....558

A queue is FIFO—first in, first out....559

A stack is LIFO—last in, first out....560

CollectionView is a MAUI control built for displaying collections....566

ObservableCollection is a collection made for data binding....567

Add your Card class to the project....568

Use XAML to instantiate your objects for data binding....571

Modify your app to use a resource Dictionary....572

Modify the event handlers to use the resource Dictionary....574

Use what you’ve learned to build an app with two decks....575

Unity Lab #4....581

Add a score that goes up when the player clicks a ball....582

Add two different modes to your game....583

Add game mode to your game....584

Add a UI to your game....586

Set up the Text that will display the score in the UI....587

Add a Button that calls a method to start the game....588

Make the Play Again button and Score Text work....589

Finish the code for the game....590

Get creative!....594

Chapter 9....595

Jimmy’s a Captain Amazing superfan…....596

…but his collection’s all over the place....597

Use LINQ to query your collections....598

LINQ works with any sequence....600

LINQ’s query syntax....603

LINQ works with objects....605

Use a LINQ query to finish the app for Jimmy....606

The var keyword lets C# figure out variable types for you....608

LINQ is versatile....614

LINQ queries aren’t run until you access their results....615

Use a group query to separate your sequence into groups....616

Use join queries to merge data from two sequences....619

Use the new keyword to create anonymous types ....620

Unit tests help you make sure your code works....629

Start writing your first test method....630

Give your unit tests access to the classes they’re testing....631

One project can only access public classes in another project....632

Use the Arrange-Act-Assert pattern to write an effective test....633

Finish your first unit test....634

Write a unit test for the GetReviews method....636

Write unit tests to handle edge cases and weird data....637

Use the => operator to create lambda expressions....640

Refactor a clown with lambdas....642

Use the ?: operator to make your lambdas make choices....645

LINQ queries are made up of methods....646

LINQ declarative syntax can be refactored into chained methods....648

Use the => operator to create switch expressions....651

Explore the Enumerable class....655

Create an enumerable sequence by hand....656

Use yield return to create your own sequences....657

Use yield return to refactor ManualSportSequence....658

Downloadable exercise: Go Fish....662

Chapter 10....663

.NET uses streams to read and write data....664

Different streams read and write different things....665

A FileStream reads and writes bytes in a file....666

Write text to a file in three simple steps....667

The Swindler launches another diabolical plan....668

Use a StreamReader to read a file....671

Data can go through more than one stream....672

Use the static File and Directory classes to work with files and directories....676

IDisposable makes sure objects are closed properly....679

Avoid filesystem errors with using statements....680

Use a MemoryStream to stream data to memory....681

What happens to an object when it’s serialized?....687

But what exactly IS an object’s state?What needs to be saved?....688

When an object is serialized, all of the objects it refers to get serialized too…....689

Use JsonSerializer to serialize your objects....690

JSON only includes data, not specific C# types....693

Next up: we’ll take a deep dive into our data....695

C# strings are encoded with Unicode....697

Visual Studio works really well with Unicode....699

.NET uses Unicode to store characters and text ....700

C# can use byte arrays to move data around....702

Use a BinaryWriter to write binary data....703

Use BinaryReader to read the data back in....704

A hex dump lets you see the bytes in your files....706

Use StreamReader to build a hex dumper....707

Use Stream.Read to read bytes from a stream....708

Modify your hex dumper to read directly from the stream....709

Run your app from the command line....710

Pass command-line arguments to an app run in the IDE....711

Downloadable exercise: Hide and Seek....714

Unity Lab #5....715

Create a new Unity project and start to set up the scene....716

Set up the camera....717

Create a GameObject for the player....718

Introducing Unity’s navigation system....719

Install the AI Navigation package....720

Things you’ll do with navigation....721

Set up the NavMesh....722

Make your player automatically navigate the play area....725

Chapter 11....728

The life and death of an object....732

Use the GC class (with caution) to force garbage collection....733

Your last chance to DO something…your object’s finalizer....734

When EXACTLY does a finalizer run?....735

Finalizers can’t depend on other objects....737

A struct looks like an object…....741

Values get copied; references get assigned....742

Structs are value types; objects are reference types....743

The stack vs. the heap: more on memory....745

Use out parameters to make a methodreturn more than one value....748

Pass by reference using the ref modifier ....749

Use optional parameters to set default values....750

A null reference doesn’t refer to any object....751

Non-nullable reference types help you avoid NREs....752

Nullable value types can be null…and handled safely....755

The null-coalescing operator ?? checks for nulls automatically....756

“Captain” Amazing…not so much....757

Records give your objects value equality automatically....759

Don’t modify records—copy them....760

Extension methods add new behavior to EXISTING classes....765

Extending a fundamental type: string....766

Chapter 12....773

Your hex dumper reads a filenamefrom the command line....774

When your program throws an exception, the CLR generates an Exception object....778

All Exception objects inherit from System.Exception....779

There are some files you just can’t dump....782

What happens when a method you want to call is risky?....783

Handle exceptions with try and catch....784

Use the debugger to follow the try/catch flow....785

If you have code that ALWAYS needs to run, use a finally block....786

Catch-all exceptions handle System.Exception....787

Use the right exception for the situation....792

Exception filters help you create precise handlers....796

The worst catch block EVER: catch-all plus comments....798

Temporary solutions are OK (temporarily)....799

Use NuGet to add a logging library to your app....801

Add logging to your ExceptionExperiment app....802

Unity Lab #6....805

Let’s pick up where the last Unity Lab left off....806

Add a platform to your scene....807

Use bake options to make the platform walkable....808

Include the stairs and ramp in the NavMesh....809

Make the player navigate around the obstacles....811

Get creative!....812

Downloadable exercise: animal match boss battle....813

Thank you for reading our book!....814

Index....815

Create apps, games, and more using this engaging, highly visual introduction to C#, .NET, and Visual Studio. In the first chapter you'll dive right in, building a fully functional game using C# and .NET MAUI that can run on Windows, Mac, and even Android and iOS devices. You'll learn how to use classes and object-oriented programming, create 3D games in Unity, and query data with LINQ. And you'll do it all by solving puzzles, doing hands-on exercises, and building real-world applications. Interested in a development career? You'll learn important development techniques and ideas—many who learned to code with this book are now professional developers, team leads, coding streamers, and more. There's no experience required except the desire to learn. And this is the best place to start.

What's so special about this book?

If you've read a Head First book, you know what to expect: a visually rich format designed for the way your brain works. If you haven't, you're in for a treat. With this book, you'll learn C# through a multisensory experience that engages your mind—rather than a text-heavy approach that puts you to sleep.