book

Head First C#, 2nd Edition

by Andrew Stellman, Jennifer Greene

May 2010

Beginner

837 pages

23h 12m

English

O'Reilly Media, Inc.

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Who is this book for?Who should probably back away from this book?We know what you’re thinkingAnd we know what your brain is thinkingMetacognition: thinking about thinkingHere’s what WE didHere’s what YOU can do to bend your brain into submissionWhat you need for this bookRead meThe technical review teamAcknowledgmentsSafari® Books Online
Why you should learn C#Here’s what the IDE automates for you...What you get with Visual Studio and C#...C# and the Visual Studio IDE make lots of things easyHelp the CEO go paperlessGet to know your users’ needs before you start building your programHere’s what you’re going to buildWhat you do in Visual Studio...What Visual Studio does for you...Develop the user interfaceVisual Studio, behind the scenesAdd to the auto-generated codeYou can already run your applicationWhere are my files?Here’s what we’ve done so far.NET Visual ObjectsWe need a database to store our informationThe IDE created a databaseSQL is its own languageCreating the table for the Contact ListThe blanks on the contact card are columns in our People tableFinish building the tableInsert your card data into the databaseConnect your form to your database objects with a data sourceAdd database-driven controls to your formGood programs are intuitive to useTest driveThe IDE builds first, then runsHow to turn YOUR application into EVERYONE’S applicationGive your users the applicationYou’re NOT done: test your installationYou’ve built a complete data-driven application
When you’re doing this......the IDE does thisWhere programs come fromEvery program starts out as source code filesThe .NET Framework gives you the right tools for the jobBuild the program to create an executableYour program runs inside the CLRThe IDE helps you codeWhen you change things in the IDE, you’re also changing your codeWait, wait! What did that say?Anatomy of a programLet’s take a closer look at your codeYour program knows where to startYou can change your program’s entry pointSo what happened?Two classes can be in the same namespaceYour programs use variables to work with dataDeclare your variablesVariables varyYou have to assign values to variables before you use themA few useful typesC# uses familiar math symbolsUse the debugger to see your variables changeLoops perform an action over and overUse a code snippet to write simple for loopsTime to start codingAdd statements to show a messageif/else statements make decisionsSet up conditions and see if they’re trueUse logical operators to check conditionsSet a variable and then check its valueAdd another conditional testAdd loops to your program
How Mike thinks about his problemsHow Mike’s car navigation system thinks about his problemsMike’s Navigator class has methods to set and modify routesSome methods have a return valueUse what you’ve learned to build a program that uses a classSo what did you just build?Mike gets an ideaHe could create three different Navigator classes...Mike can use objects to solve his problemYou use a class to build an objectAn object gets its methods from its classWhen you create a new object from a class, it’s called an instance of that classA better solution...brought to you by objects!Theory and practiceA little advice for the code exercisesAn instance uses fields to keep track of thingsMethods are what an object does. Fields are what the object knowsLet’s create some instances!Thanks for the memoryLet’s take a closer look at what happened hereWhat’s on your program’s mindYou can use class and method names to make your code intuitiveGive your classes a natural structureLet’s build a class diagramClass diagrams help you organize your classes so they make senseBuild a class to work with some guysCreate a project for your guysBuild a form to interact with the guysThere’s an easier way to initialize objects

The variable’s type determines what kind of data it can storeA variable is like a data to-go cup10 pounds of data in a 5 pound bagEven when a number is the right size, you can’t just assign it to any variableSo what happened?When you cast a value that’s too big, C# will adjust it automaticallyC# does some casting automaticallyWhen you call a method, the arguments must be compatible with the types of the parametersCombining = with an operatorObjects use variables, tooRefer to your objects with reference variablesReferences are like labels for your objectIf there aren’t any more references, your object gets garbage-collectedMultiple references and their side effectsTwo references means TWO ways to change an object’s dataA special case: arraysUse each element in an array like it is a normal variableArrays can contain a bunch of reference variables, tooWelcome to Sloppy Joe’s Budget House o’ Discount Sandwiches!Objects use references to talk to each otherWhere no object has gone beforeBuild a typing game
Kathleen is an event plannerWhat does the estimator do?Kathleen’s Test DriveEach option should be calculated individuallyIt’s easy to accidentally misuse your objectsEncapsulation means keeping some of the data in a class privateUse encapsulation to control access to your class’s methods and fieldsBut is the realName field REALLY protected?Private fields and methods can only be accessed from inside the classEncapsulation makes your classes...Mike’s navigator program could use better encapsulationThink of an object as a black boxEncapsulation keeps your data pristineA quick example of encapsulationProperties make encapsulation easierBuild an application to test the Farmer classUse automatic properties to finish the classFully encapsulate the Farmer classWhat if we want to change the feed multiplier?Use a constructor to initialize private fields
Kathleen does birthday parties, tooWe need a BirthdayParty classHere’s what we’re going to do:Build the Party Planner version 2.0One more thing...can you add a $100 fee for parties over 12?When your classes use inheritance, you only need to write your code onceDinner parties and birthday parties are both partiesBuild up your class model by starting general and getting more specificHow would you design a zoo simulator?Use inheritance to avoid duplicate code in subclassesDifferent animals make different noisesThink about what you need to overrideThink about how to group the animalsCreate the class hierarchyEvery subclass extends its base classC# always calls the most specific methodUse a colon to inherit from a base classWe 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 methods it inheritedAny place where you can use a base class, you can use one of its subclasses insteadA subclass can hide methods in the superclassHiding methods versus overriding methodsUse different references to call hidden methodsUse the new keyword when you’re hiding methodsUse the override and virtual keywords to inherit behaviorA subclass can access its base class using the base keywordWhen a base class has a constructor, your subclass needs one, tooThe base class constructor is executed before the subclass constructorNow you’re ready to finish the job for Kathleen!Build a beehive management systemFirst you’ll build the basic systemUse inheritance to extend the bee management system
Let’s get back to bee-sicsLots of things are still the sameWe can use inheritance to create classes for different types of beesAn interface tells a class that it must implement certain methods and propertiesUse the interface keyword to define an interfaceNow you can create an instance of NectarStinger that does both jobsClasses that implement interfaces have to include ALL of the interface’s methodsGet a little practice using interfacesYou can’t instantiate an interface, but you can reference an interfaceInterface references work just like object referencesYou can find out if a class implements a certain interface with “is”Interfaces can inherit from other interfacesAny class that implements an interface that inherits from IWorker must implement its methods and propertiesThe RoboBee 4000 can do a worker bee’s job without using valuable honeyis tells you what an object implements, as tells the compiler how to treat your objectA CoffeeMaker is also an ApplianceUpcasting works with both objects and interfacesDowncasting lets you turn your appliance back into a coffee makerWhen downcasting fails, as returns nullUpcasting and downcasting work with interfaces, tooThere’s more than just public and privateAccess modifiers change visibilitySome classes should never be instantiatedAn abstract class is like a cross between a class and an interfaceLike we said, some classes should never be instantiatedSolution: use an abstract classAn abstract method doesn’t have a bodyThe four principles of object oriented programmingPolymorphism means that one object can take many different formsKeep your eyes open for polymorphism in the next exercise!
Strings don’t always work for storing categories of dataEnums let you work with a set of valid valuesEnums let you represent numbers with namesWe could use an array to create a deck of cards......but what if you wanted to do more?Arrays are hard to work withLists make it easy to store collections of...anythingLists are more flexible than arraysLists shrink and grow dynamicallyGenerics can store any typeCollection initializers work just like object initializersLet’s create a List of DucksHere’s the initializer for your List of DucksLists are easy, but SORTING can be trickyYou could sort a list of ducks by size......or by kindLists know how to sort themselvesIComparable<Duck> helps your list sort its ducksAn object’s CompareTo() method compares it to another objectUse IComparer to tell your List how to sortCreate an instance of your comparer objectMultiple IComparer implementations, multiple ways to sort your objectsIComparer can do complex comparisonsOverriding a ToString() method lets an object describe itselfUpdate your foreach loops to let your Ducks and Cards print themselvesAdd a ToString() method to your Card object, tooYou can upcast an entire list using IEnumerableCombine your birds into a single listYou can build your own overloaded methodsUse a dictionary to store keys and valuesThe Dictionary Functionality RundownYour key and value can be different typesBuild a program that uses a DictionaryAnd yet MORE collection types...Generic collections are an important part of the .NET FrameworkA queue is FIFO—First In, First OutA stack is LIFO—Last In, First Out
.NET uses streams to read and write dataDifferent streams read and write different thingsThings you can do with a streamA FileStream reads and writes bytes to a fileHow to write text to a file in 3 simple stepsThe Swindler launches another diabolical planReading and writing using two objectsData can go through more than one streamUse built-in objects to pop up standard dialog boxesShowDialog() pops up a dialog boxDialog boxes are just another .NET controlDialog boxes are objects, tooUse the built-in File and Directory classes to work with files and directoriesThings you can do with a FileThings you can do with a DirectoryUse file dialogs to open and save files (all with just a few lines of code)IDisposable makes sure your objects are disposed of properlyAvoid file system errors with using statementsUse multiple using statements for multiple objectsTrouble at workYou can help Brian out by building a program to manage his excusesWriting files usually involves making a lot of decisionsUse a switch statement to choose the right optionUse a switch statement to let your deck of cards read from a file or write itself out to oneAdd an overloaded Deck() constructor that reads a deck of cards in from a fileWhat 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...Serialization lets you read or write a whole object all at onceYou’ll need a BinaryFormatter objectNow just create a stream and read or write your objectsIf you want your class to be serializable, mark it with the [Serializable] attributeLet’s serialize and deserialize a deck of cards.NET uses Unicode to store characters and textC# can use byte arrays to move data aroundUse a BinaryWriter to write binary dataUse BinaryReader to read the data back inYou can read and write serialized files manually, tooFind where the files differ, and use that information to alter themWorking with binary files can be trickyUse file streams to build a hex dumperHow to make a hex dumpWorking with hexStreamReader and StreamWriter will do just fine (for now)Use Stream.Read() to read bytes from a stream
Brian needs his excuses to be mobileBut the program isn’t working!When your program throws an exception, .NET generates an Exception objectBrian’s code did something unexpectedAll exception objects inherit from ExceptionThe debugger helps you track down and prevent exceptions in your codePut your IDE into Expert mode to expand the Debug toolbarToggle hexadecimal mode on and offUse the IDE’s debugger to ferret out exactly what went wrong in the Excuse ManagerUh oh—the code’s still got problems...Handle exceptions with try and catchWhat happens when a method you want to call is risky?Use the debugger to follow the try/catch flowIf you have code that ALWAYS should run, use a finally blockUse the Exception object to get information about the problemUse more than one catch block to handle multiple types of exceptionsOne class throws an exception, another class catches the exceptionBees need an OutOfHoney exceptionAn easy way to avoid a lot of problems: using gives you try and finally for freeException avoidance: implement IDisposable to do your own cleanupThe worst catch block EVER: catch-all plus commentsYou should handle your exceptions, not bury themTemporary solutions are OK (temporarily)A few simple ideas for exception handlingBrian finally gets his vacation......and things are looking up back home!
Ever wish your objects could think for themselves?But how does an object KNOW to respond?When an EVENT occurs...objects listenWant to DO SOMETHING with an event? You need an event handlerOne object raises its event, others listen for it...Then, the other objects handle the eventConnecting the dotsUse a standard name when you add a method to raise an eventThe IDE creates event handlers for you automaticallyGeneric EventHandlers let you define your own event typesUse implicit conversion by leaving out the new keyword and the event typeThe forms you’ve been building all use eventsOne event, multiple handlersConnecting event senders with event receivers“My people will get in touch with your people.”A delegate STANDS IN for an actual methodA delegate adds a new type to your projectDelegates in actionAn object can subscribe to an event......but that’s not always a good thing!Use a callback to control who’s listeningA callback is just a way to use delegates
You’ve come a long way, babyWe’ve also become beekeepersBut we can do a lot better now...The beehive simulator architectureBuilding the beehive simulatorLife and death of a flowerNow we need a Bee classP. A. H. B. (Programmers Against Homeless Bees)The hive runs on honeyFilling out the Hive classThe hive’s Go() methodWe’re ready for the WorldThe World object keeps everything Go()ingWe’re building a turn-based systemHere’s the code for WorldGiving the bees behaviorThe main form tells the world to Go()We can use World to get statisticsTimers fire events over and over againThe timer’s using an event handler behind the scenesAdd a timer to the simulatorTest driveLet’s work with groups of beesA collection collects...DATALINQ makes working with data in collections and databases easyTest drive (Part 2)One final challenge: Open and Save
You’ve been using controls all along to interact with your programsForm controls are just objectsUse controls to animate the beehive simulatorAdd a renderer to your architectureThe renderer draws everything in the world on the two formsThe simulator renders the world after each frameControls are well suited for visual display elementsBuild your first animated controlWe want a control in the toolboxBeeControl is LIKE a PictureBox...so let’s start by INHERITING from PictureBoxCreate a button to add the BeeControl to your formYour controls need to dispose their controls, too!A UserControl is an easy way to build a controlYour simulator’s renderer will use your BeeControl to draw animated bees on your formsAdd the hive and field forms to the projectFigure out where your locations areBuild the rendererNow connect the main form to your two new forms, HiveForm and FieldFormTest drive...ahem...buzzLooks great, but something’s not quite right...Let’s take a closer look at those performance issuesYou resized your Bitmaps using a Graphics objectLet’s see image resizing in actionYour image resources are stored in Bitmap objectsThen each Bitmap is drawn to the screenThe bigger they are...Use System.Drawing to TAKE CONTROL of graphics yourselfA 30-second tour of GDI+ graphicsUse graphics to draw a picture on a formGraphics can fix our transparency problem...Use the Paint event to make your graphics stickA closer look at how forms and controls repaint themselvesDouble buffering makes animation look a lot smootherDouble buffering is built into forms and controlsOverhaul the beehive simulatorUse a Graphics object and an event handler for printingPrintDocument works with the print dialog and print preview window objectsUse e.HasMorePages to print multipage documents
Your last chance to DO something... your object’s finalizerWhen EXACTLY does a finalizer run?You can SUGGEST to .NET that it’s time to collect the garbageDispose() works with using, finalizers work with garbage collectionFinalizers can’t depend on stabilityMake an object serialize itself in its Dispose()A struct looks like an object......but isn’t an objectValues get copied; references get assignedStructs are value types; objects are reference typesHere’s what happened...The stack vs. the heap: more on memoryUse out parameters to make a method return more than one valuePass by reference using the ref modifierUse optional parameters to set default valuesUse nullable types when you need nonexistent valuesNullable types help you make your programs more robustCaptain Amazing...not so muchExtension methods add new behavior to EXISTING classesExtending a fundamental type: string
An easy project......but the data’s all over the placeLINQ can pull data from multiple sources.NET collections are already set up for LINQLINQ makes queries easyLINQ is simple, but your queries don’t have to beLINQ is versatileLINQ can combine your results into groupsCombine Jimmy’s values into groupsUse join to combine two collections into one queryJimmy saved a bunch of doughConnect LINQ to a SQL databaseUse a join query to connect Starbuzz and Objectville
#1. The Basics...more basics...#2. Namespaces and assemblies...so what did I just do?Why you added public to the class declarations in Chapter 13#3. Use BackgroundWorker to make your UI responsive#4. The Type class and GetType()#5. Equality, IEquatable, and Equals()#6. Using yield return to create enumerable objects#7. RefactoringExtract a methodRename a variableConsolidate a conditional expression#8. Anonymous types, anonymous methods, and lambda expressions#9. Serializing data using DataContractSerializer#10. LINQ to XMLSave and load XML filesQuery your dataRead data from an RSS feed#11. Windows Presentation FoundationDid you know that C# and the .NET Framework can...

Overview

You want to learn C# programming, but you're not sure you want to suffer through another tedious technical book. You're in luck: Head First C# introduces this language in a fun, visual way. You'll quickly learn everything from creating your first program to learning sophisticated coding skills with C# 4.0, Visual Studio 2010 and .NET 4, while avoiding common errors that frustrate many students.

The second edition offers several hands-on labs along the way to help you build and test programs using skills you've learned up to that point. In the final lab, you'll put everything together. From objects to garbage collection and from exceptions to interactions, you'll learn C# in a way that engages and entertains your brain. Here are a few of the topics you'll learn:

Start by building a useful application with pre-built components in Visual Studio 2010
Discover how objects work, using real-world examples
Store numbers, text, and other basic data types using primitives
Save complex data in files and databases with great C# tools
Build intuitive and easy-to-use interfaces by following simple rules
Design your code to catch exceptions -- things you don't expect
Develop good programming habits, such as refactoring code and applying unit tests
Learn how web services put your programs in touch with the rest of the world
Make it easy for other people to install your software