What will you learn from this book?
Ready to dive into C#? This practical guide provides beginning programmers with a fun and highly visual introduction to C#, XAML, .NET Core, and Visual Studio. You’ll quickly learn C# fundamentals, including how this language helps you create user interfaces, databases, and more. With this latest edition, you’ll build a fully functional game in the opening chapter and then learn how to use classes and object-oriented programming, draw graphics and animation, and query data with LINQ. And you’ll do it all by creating games, solving puzzles, and doing hands-on projects. By the time you’re done, you’ll be a solid C# programmer—and you’ll have a great time along the way!
- Dive right in—build a game with C# in the first chapter
- Learn how to use XAML to design attractive and interactive pages and windows
- Use any edition of Visual Studio to practice your C# coding skills in dozens of projects
- Create cross-platform apps and build native macOS apps using Visual Studio 2019 for Mac
- Develop 3D games and simulations in specially designed Unity labs using C# tools, techniques, and concepts
Why does this book look so different?
Based on the latest research in cognitive science and learning theory, Head First C# uses a visually rich format to engage your mind rather than a text-heavy approach that puts you to sleep. Why waste your time struggling with new concepts? This multisensory learning experience is designed for the way your brain really works.
Table of Contents
1. Start Building with c#: Build something great…fast!
2. Dive into C#: Statements, Classes, and Code
3. Objects…get oriented!: Making code make sense
4. Types and References: Getting the Reference
5. Encapsulation: Keep your Privates… Private
6. Inheritance: Your Object’s Family Tree
7. Interfaces, Casting, and “is”: Making Classes keep their Promises
8. Enums and Collections: Organizing your Data
9. LINQ and lambdas: Get control of your data
10. Reading and writing files: Save the last byte for me!
11. Captain Amazing: The Death of the Object
12. Exception Handling: Putting out Fires Gets old
A. ASP.NET Core Blazor projects: Visual Studio for Mac Learner’s Guide
B. Code Kata Guide for the Advanced and/or Impatient
Table of Contents (the real thing) Intro: How to use this book Who is this book for? Who should probably avoid this book? We know what you’re thinking. And we know what your brain is thinking. Metacognition: thinking about thinking Here’s what WE did Here’s what YOU can do to bend your brain into submission README The technical review team Acknowledgments And finally... O’Reilly online learning 1. Start Building with c#: Build something great…fast! Why you should learn C# Visual Studio is your gateway to C# If you’re on Windows... If you’re on a Mac... Visual Studio is a tool for writing code and exploring C# Create your first project in Visual Studio Let’s build a game! Your animal matching game is a WPF app Here’s how you’ll build your game Create a WPF project in Visual Studio Visual Studio created a project folder full of files for you Use XAML to design your window Design the window for your game Set the window size and title with XAML properties Add rows and columns to the XAML grid Make the rows and columns equal size Add a TextBlock control to your grid Now you’re ready to start writing code for your game Generate a method to set up the game Finish your SetUpGame method Run your program Add your new project to source control The next step to build the game is handling mouse clicks Make your TextBlocks respond to mouse clicks Add the TextBlock_MouseDown code Make the rest of the TextBlocks call the same MouseDown event handler Finish the game by adding a timer Add a timer to your game’s code Use the debugger to troubleshoot the exception Add the rest of the code and finish the game Update your code in source control Even better ifs… 2. Dive into C#: Statements, Classes, and Code Let’s take a closer look at the files for a console app A statement performs one single action Two classes can be in the same namespace (and file!) Statements are the building blocks for your apps Your programs use variables to work with data Declare your variables Variables vary You need to assign values to variables before you use them A few useful types Generate a new method to work with variables Add code that uses operators to your method Use the debugger to watch your variables change Use operators to work with variables “if” statements make decisions if/else statements also do something if a condition isn’t true Loops perform an action over and over while loops keep looping statements while a condition is true do/while loops run the statements then check the condition for loops run a statement after each loop Use code snippets to help write loops Controls drive the mechanics of your user interfaces Create a WPF app to experiment with controls Add a TextBox control to your app Add C# code to update the TextBlock Add an event handler that only allows number input Add sliders to the bottom row of the grid Add C# code to make the rest of the controls work Unity Lab #1: Explore C# with Unity Unity is a powerful tool for game design Download Unity Hub Use Unity Hub to create a new project Make Visual Studio your Unity script editor Take control of the Unity layout Choose the Wide layout to match our screenshots Your scene is a 3D environment Unity games are made with GameObjects Use the Move Gizmo to move your GameObjects The Inspector shows your GameObject’s components Add a material to your Sphere GameObject Rotate your sphere Move the Scene view camera with the Hand tool and Scene Gizmo Get creative! 3. Objects…get oriented!: Making code make sense If code is useful, it gets reused Some methods take parameters and return a value Let’s build a program that picks some cards Create your PickRandomCards console app Finish your PickSomeCards method Your finished CardPicker class Ana’s working on her next game Ana’s game is evolving… Build a paper prototype for a classic game Up next: build a WPF version of your card picking app A StackPanel is a container that stacks other controls Reuse your CardPicker class in a new WPF app Use a Grid and StackPanel to lay out the main window Lay out your Card Picker desktop app’s window Ana’s prototypes look great… …but what if she wants more than one enemy? Ana can use objects to solve her problem You use a class to build an object An object gets its methods from its class When you create a new object from a class, it’s called an instance of that class A better solution for Ana…brought to you by objects Theory and practice An instance uses fields to keep track of things Methods are what an object does. Fields are what the object knows. Thanks for the memory What’s on your program’s mind Sometimes code can be difficult to read Extremely compact code can be especially problematic Most code doesn’t come with a manual Use intuitive class and method names Build a class to work with some guys There’s an easier way to initialize objects with C# Use the C# Interactive window to run C# code 4. Types and References: Getting the Reference Owen could use our help! Storytelling, fantasy, and mechanics Character sheets store different types of data on paper A variable’s type determines what kind of data it can store C# has several types for storing integers Types for storing really HUGE and really tiny numbers Let’s talk about strings A literal is a value written directly into your code Use suffixes to give your literals types A variable is like a data to-go cup Use the Convert class to explore bits and bytes Other types come in different sizes, too 10 pounds of data in a 5-pound bag Casting lets you copy values that C# can’t automatically convert to another type So what happened? When you cast a value that’s too big,C# adjusts it to fit its new container C# does some conversions automatically When you call a method, the arguments need to be compatible with the types of the parameters Owen is constantly improving his game… …but the trial and error can be time-consuming Let’s help Owen experiment with ability scores Use the C# compiler to find the problematic line of code Add a cast to get the AbilityScoreCalculator class to compile... …but there’s still a bug! And now we can finally fix Owen’s bug Use reference variables to access your objects References are like sticky notes for your objects If there aren’t any more references,your object gets garbage-collected Multiple references and their side effects Two references mean TWO variables that can change the same object’s data Objects use references to talk to each other Arrays hold multiple values Use each element in an array like it’s a normal variable Arrays can contain reference variables null means a reference points to nothing Welcome to Sloppy Joe’s Budget House o’ Discount Sandwiches! Unity Lab #2: Write C# Code for Unity C# scripts add behavior to your GameObjects Add a C# script to your GameObject Write C# code to rotate your sphere Add a breakpoint and debug your game Use a hit count to skip frames Use the debugger to understand Time.deltaTime Add a cylinder to show where the Y axis is Add fields to your class for the rotation angle and speed Use Debug.DrawRay to explore how 3D vectors work Use Unity to visualize vectors in 3D Run the game to see the ray in the Scene view Add a duration to the ray so it leaves a trail Rotate your ball around a point in the scene Use Unity to take a closer look at rotation and vectors Get creative! 5. Encapsulation: Keep your Privates… Private Let’s help Owen roll for damage Create a console app to calculate damage Design the XAML for a WPF version of the damage calculator The code-behind for the WPF damage calculator Tabletop talk (or maybe…dice discussion?) Let’s try to fix that bug Use Debug.WriteLine to print diagnostic information It’s easy to accidentally misuse your objects Encapsulation means keeping some of the data in a class private Use encapsulation to control access to your class’s methods and fields But is the RealName field REALLY protected? Private fields and methods can only be accessed from instances of the same class Why encapsulation? Think of an object as a black box… Encapsulation makes your classes… A few ideas for encapsulating classes Let’s use encapsulation to improve the SwordDamage class Is every member of the SwordDamage class public? Are fields or methods being misused? Is there calculation required after setting a field? So what fields and methods really need to be public? Encapsulation keeps your data safe Let’s use encapsulation in a class Write a console app to test the PaintballGun class Our class is well-encapsulated, but... Properties make encapsulation easier Replace the GetBalls and SetBalls methods with a property Modify your Main method to use the Balls property Debug your PaintballGun class to understand how the property works Auto-implemented properties simplify your code Use the prop snippet to create an auto-implemented property Use a private setter to create a read-only property Make the BallsLoaded setter private What if we want to change the magazine size? But there’s a problem…how do we initialize MagazineSize? Use a constructor with parameters to initialize properties Specify arguments when you use the “new” keyword A few useful facts about methods and properties 6. Inheritance: Your Object’s Family Tree Calculate damage for MORE weapons Use a switch statement to match several candidates One more thing...can we calculate damage for a dagger? and a mace? and a staff? and... When your classes use inheritance, you only need to write your code once Build up your class model by starting general and getting more specific How would you design a zoo simulator? Different animals have different behaviors Every subclass extends its base class C# always calls the most specific method Any place where you can use a base class, you can use one of its subclasses instead Use a colon to extend a base class We know that inheritance adds the base class fields, properties, and methods to the subclass... ...but some birds don’t fly! A subclass can override methods to change or replace members it inherited Some members are only implemented in a subclass Use the debugger to understand how overriding works Build an app to explore virtual and override A subclass can hide methods in the base class Hiding methods versus overriding methods Use the new keyword when you’re hiding methods Use different references to call hidden methods Use the override and virtual keywords to inherit behavior A subclass can access its base class using the base keyword When a base class has a constructor, your subclass needs to call it A subclass and base class can have different constructors It’s time to finish the job for Owen When your classes overlap as little as possible, that’s an important design principle called separation of concerns Use the debugger to really understand how these classes work Build a beehive management system The beehive management system class model The Queen class: how she manages the worker bees The UI: add the XAML for the main window Feedback drives your Beehive Management game Workers and honey are in a feedback loop The Beehive Management System is turn-based...now let’s convert it to real-time Some classes should never be instantiated An abstract class is an intentionally incomplete class Like we said, some classes should never be instantiated Solution: use an abstract class An abstract method doesn’t have a body Abstract properties work just like abstract methods Unity Lab #3: GameObject Instances Let’s build a game in Unity! Create a new material inside the Materials folder Spawn a billiard ball at a random point in the scene Use the debugger to understand Random.value Turn your GameObject into a prefab Create a script to control the game Attach the script to the Main Camera Press Play to run your code Watch the live instances in the Hierarchy window Use the Inspector to work with GameObject instances Use physics to keep balls from overlapping Get creative! 7. Interfaces, Casting, and “is”: Making Classes keep their Promises The beehive is under attack! So we need a DefendHive method, because enemies can attack at any time We can use casting to call the DefendHive method... ...but what if we add more Bee subclasses that can defend? An interface defines methods and properties that a class must implement... ...but there’s no limit to the number of interfaces a class can implement Interfaces let unrelated classes do the same job Get a little practice using interfaces You can’t instantiate an interface, but you can reference an interface If you try to instantiate an interface, your code won’t build Use the interface to reference an object you already have Interface references are ordinary object references The RoboBee 4000 can do a worker bee’s job without using valuable honey The IWorker’s Job property is a hack Use “is” to check the type of an object Use “is” to access methods in a subclass What if we want different animals to swim or hunt in packs? Use interfaces to work with classes that do the same job Use the “is” keyword to check if the Animal is a swimmer or pack hunter Safely navigate your class hierarchy with “is” C# has another tool for safe type conversion: the “as” keyword Use upcasting and downcasting to move up and down a class hierarchy A quick example of upcasting Upcasting turns your CoffeeMaker into an Appliance Downcasting turns your Appliance back into a CoffeeMaker Upcasting and downcasting work with interfaces, too Interfaces can inherit from other interfaces Interfaces can have static members Default implementations give bodies to interface methods Add a ScareAdults method with a default implementation Data binding updates WPF controls automatically Modify the Beehive Management System to use data binding Polymorphism means that one object can take many different forms Keep your eyes open for polymorphism! The four core principles of object-oriented programming 8. Enums and Collections: Organizing your Data Strings don’t always work for storing categories of data Enums let you work with a set of valid values An enum defines a new type Enums let you represent numbers with names We could use an array to create a deck of cards... ...but what if you wanted to do more? Arrays can be annoying to work with Lists make it easy to store collections of...anything Lists are more flexible than arrays Let’s build an app to store shoes Generic collections can store any type Generic lists are declared using
Collection initializers are similar to object initializers Let’s create a List of Ducks Here’s the initializer for your List of Ducks Lists are easy, but SORTING can be tricky Lists know how to sort themselves IComparable helps your List sort its Ducks An object’s CompareTo method compares it to another object Use IComparer to tell your List how to sort Add an IComparer to your project Create an instance of your comparer object Multiple IComparer implementations, multiple ways to sort your objects Comparers can do complex comparisons Overriding a ToString method lets an object describe itself Override the ToString method to see your Ducks in the IDE Update your foreach loops to let your Ducks and Cards write themselves to the console Add a ToString method to your Card object, too You can upcast an entire list using IEnumerable Use a Dictionary to store keys and values The Dictionary functionality rundown Your key and value can be different types Build a program that uses a dictionary And yet MORE collection types... Generic .NET collections implement IEnumerable A queue is FIFO—first in, first out A stack is LIFO—last in, first out Unity Lab #4: User Interfaces Add a score that goes up when the player clicks a ball Add two different modes to your game Add game mode to your game Add a UI to your game Use the 2D view to work with the Canvas Set up the Text that will display the score in the UI Add a button that calls a method to start the game Make the Play Again button and Score Text work Finish the code for the game Get creative! 9. LINQ and lambdas: Get control of your data Jimmy’s a Captain Amazing super-fan... ...but his collection’s all over the place Use LINQ to query your collections LINQ works with any IEnumerable LINQ methods enumerate your sequences LINQ’s query syntax LINQ queries are built from clauses LINQ works with objects Use a LINQ query to finish the app for Jimmy The var keyword lets C# figure out variable types for you When you use var, C# figures out the variable’s type automatically LINQ is versatile LINQ queries aren’t run until you access their results Use a group query to separate your sequence into groups Use join queries to merge data from two sequences Use the new keyword to create anonymous types Unit tests help you make sure your code works Visual Studio for Windows has a Test Explorer window Visual Studio for Mac has the Unit Tests tool window Add a unit test project to Jimmy’s comic collection app Write your first unit test Write a unit test for the GetReviews method Write unit tests to handle edge cases and weird data Use the => operator to create lambda expressions A lambda test drive Refactor a clown with lambdas Use the ?: operator to make your lambdas make choices Lambda expressions and LINQ Use lambda expressions with methods that take a Func parameter LINQ queries can be written as chained LINQ methods The OrderBy LINQ method sorts a sequence The Where LINQ method pulls out a subset of a sequence Use the => operator to create switch expressions Explore the Enumerable class Enumerable.Empty creates an empty sequence of any type Enumerable.Repeat repeats a value a number of times So what exactly is an IEnumerable ? Create an enumerable sequence by hand Use yield return to create your own sequences Use the debugger to explore yield return Use yield return to refactor ManualSportSequence Add an indexer to BetterSportSequence Collectioncross Collectioncross Solution 10. Reading and writing files: Save the last byte for me! .NET uses streams to read and write data Different streams read and write different things Things you can do with a stream: A FileStream reads and writes bytes in a file Write text to a file in three simple steps The Swindler launches another diabolical plan StreamWriter Magnets StreamWriter Magnets Solution Use a StreamReader to read a file Data can go through more than one stream Pool Puzzle Pool Puzzle Solution Use the static File and Directory classes to work with files and directories Things you can do with the static File class: Things you can do with the static Directory class: IDisposable makes sure objects are closed properly Use the IDE to explore IDisposable Avoid filesystem errors with using statements Use multiple using statements for multiple objects Use a MemoryStream to stream data to memory Use Encoding.UTF8.GetString to convert byte arrays to strings What happens to an object when it’s serialized? But what exactly IS an object’s state? What needs to be saved? When an object is serialized, all of the objects it refers to get serialized, too... Use JsonSerialization to serialize your objects JSON only includes data, not specific C# types Next up: we’ll take a deep dive into our data C# strings are encoded with Unicode Visual Studio works really well with Unicode .NET uses Unicode to store characters and text C# can use byte arrays to move data around Use a BinaryWriter to write binary data Use BinaryReader to read the data back in A hex dump lets you see the bytes in your files How to make a hex dump of some plain text Use StreamReader to build a hex dumper Use Stream.Read to read bytes from a stream Modify your hex dumper to use command-line arguments Run your app from the command line Unity Lab #5: Raycasting Create a new Unity project and start to set up the scene Set up the camera Create a GameObject for the player Introducing Unity’s navigation system Set up the NavMesh Make your player automatically navigate the play area 11. Captain Amazing: The Death of the Object The life and death of an object Use the GC class (with caution) to force garbage collection Your last chance to DO something...your object’s finalizer When EXACTLY does a finalizer run? You can SUGGEST to .NET that it’s time to collect the garbage Finalizers can’t depend on other objects Don’t use finalizers for serialization A struct looks like an object... ...but isn’t an object Values get copied; references get assigned Structs are value types; objects are reference types Here’s what happened... The stack vs. the heap: more on memory Use out parameters to make a method return more than one value Pass by reference using the ref modifier Use optional parameters to set default values A null reference doesn’t refer to any object Non-nullable reference types help you avoid NREs Use encapsulation to prevent your property from ever being null The null-coalescing operator ?? helps with nulls ?? checks for null and returns an alternative ??= assigns a value to a variable only if it’s null Nullable value types can be null...and handled safely “Captain” Amazing...not so much Pool Puzzle Pool Puzzle Solution Extension methods add new behavior to EXISTING classes Extending a fundamental type: string Extension Magnets Extension Magnets Solution 12. Exception Handling: Putting out Fires Gets old Your hex dumper reads a filename from the command line But what happens if you give HexDump an invalid filename? When your program throws an exception, the CLR generates an Exception object All Exception objects inherit from System.Exception There are some files you just can’t dump What happens when a method you want to call is risky? Handle exceptions with try and catch Use the debugger to follow the try/catch flow If you have code that ALWAYS needs to run, use a finally block Catch-all exceptions handle System.Exception Avoid catch-all exception with multiple catch blocks Pool Puzzle Pool Puzzle Solution Use the right exception for the situation Catch custom exceptions that extend System.Exception Exception Magnets Exception Magnets Solution Exception filters help you create precise handlers The worst catch block EVER: catch-all plus comments You should handle your exceptions, not bury them Temporary solutions are OK (temporarily) Unity Lab #6 Scene Navigation Let’s pick up where the last Unity Lab left off Add a platform to your scene Use bake options to make the platform walkable Include the stairs and ramp in your NavMesh Fix height problems in the NavMesh Add a NavMesh Obstacle Add a script to move the obstacle up and down Get creative! Downloadable exercise: Animal match boss battle Thank you for reading our book! But wait, there’s more! Your journey’s just begun... And check out these essential (and amazing!) books by some of our friends and colleagues, also published by O’REILLY A. ASP.NET Core Blazor projects: Visual Studio for Mac Learner’s Guide Why you should learn C# Visual Studio is your gateway to C# Install .NET Core You can also use Visual Studio for Windows to build Blazor web applications Visual Studio is a tool for writing code and exploring C# Create your first project in Visual Studio for Mac Use the Visual Studio IDE to explore your app Let’s build a game! Your animal matching game is a Blazor WebAssembly app Here’s how you’ll build your game Create a Blazor WebAssembly App in Visual Studio Run your Blazor web app in a browser Now you’re ready to start writing code for your game How the page layout in your animal matching game will work Visual Studio helps you write C# code Finish creating your emoji list and display it in the app Replace the contents of the page Shuffle the animals so they’re in a random order You’re running your game in the debugger Add your new project to source control Add C# code to handle mouse clicks Add click event handlers to your buttons Here’s the code for the event handler Hook up your event handler to the buttons Test your event handler But what happens if you click on the same button twice? Use the debugger to troubleshoot the problem Keep debugging your event handler Track down the bug that’s causing the problem... ...and fix the bug! Add code to reset the game when the player wins Finish the game by adding a timer Add a timer to your game’s code Clean up the navigation menu Even better ifs... from #dive_into_chash_statementscomma_classesc dive into C# Controls drive the mechanics of your user interfaces Create a new Blazor WebAssembly App project Create a page with a slider control Add a text input to your app Add color and date pickers to your app from #objectshellipget_orientedexclamation_mar objects...get oriented! Up next: build a Blazor version of your card picking app Reuse your CardPicker class in a new Blazor app The page is laid out with rows and columns The slider uses data binding to update a variable from #types_and_references_getting_the_referen types and references Welcome to Sloppy Joe’s Budget House o’ Discount Sandwiches! B. Code Kata Guide for the Advanced and/or Impatient Index
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