Learn C in one day and Learn It Well

LearnC#InOneDayandLearnItWell
C#forBeginnerswithHands-OnProject
TheonlybookyouneedtostartcodinginC#
immediately


ByJamieChan

/>
Copyright©2015

Allrightsreserved.Nopartofthispublicationmaybereproduced,
distributed,ortransmittedinanyformorbyanymeans,including
photocopying,recording,orotherelectronicormechanicalmethods,without
thepriorwrittenpermissionofthepublisher,exceptinthecaseofbrief
quotationsembodiedincriticalreviewsandcertainothernoncommercialuses
permittedbycopyrightlaw.



Preface

ThisbookiswrittentohelpyoulearnC#FASTandlearnitWELL.

Thebookdoesnotassumeanypriorbackgroundincoding.Ifyouarean
absolutebeginner,you’llfindthatthisbookexplainscomplexconceptsinan
easytounderstandmanner.IfyouareanexperiencedcoderbutnewtoC#,
thisbookwillprovideyouwithenoughdepthtostartcodinginC#
immediately.

Allexamplesinthebookarecarefullychosentodemonstrateeachconceptso
thatyoucangainadeeperunderstandofthelanguage.Topicsarecarefully
selectedtogiveyouabroadexposuretoC#,whilenotoverwhelmingyou
withinformationoverload.Thesetopicsincludeobject-orientedprogramming
concepts,errorhandlingtechniques,filehandlingtechniquesandmore.

Inaddition,asRichardBransonputsit:“Thebestwayoflearningabout
anythingisbydoing”.Thisbookcomeswithaprojectwhereyou’llbeguided
throughthecodingofasimplepayrollsoftwarefromscratch.Theprojectuses
conceptscoveredinthebookandgivesyouachancetoseehowitallties
together.

Youcandownloadthesourcecodefortheprojectandallthesample
programsinthisbookat
/>
ContactInformation

Iwouldlovetohearfromyou.
Forfeedbackorqueries,youcancontactmeat




MoreBooksbyJamie

Python:LearnPythoninOneDayandLearnItWell



CSS:LearnCSSinOneDayandLearnItWell

TableofContents

Chapter1:IntroductiontoC#
WhatisC#?
WhyLearnC#?

Chapter2:GettingreadyforC#
InstallingVisualStudioCommunity
YourFirstC#Program
BasicStructureofaC#Program
Directive
Namespace
TheMain()Method
Comments

Chapter3:TheWorldofVariablesandOperators
Whatarevariables?
DataTypesinC#
int
byte
float
double
decimal
char
bool
NamingaVariable
InitializingaVariable

TheAssignmentSign
BasicOperators
MoreAssignmentOperators
TypeCastingInC#

Chapter4:Arrays,StringsandLists
Array
ArrayPropertiesandMethods
String


StringPropertiesandMethods
Lists
ListPropertiesandMethods
ValueTypevs.ReferenceType

Chapter5:MakingourProgramInteractive
DisplayingMessagestoUsers
EscapeSequences
AcceptingUserInput
ConvertingaStringtoaNumber
PuttingitallTogether

Chapter6:MakingChoicesandDecisions
ConditionStatements
ControlFlowStatements
IfStatement
InlineIf
SwitchStatement
ForLoop

ForeachLoop
WhileLoop
Dowhile
JumpStatements
Break
Continue
ExceptionHandling
SpecificErrors

Chapter7:Object-OrientedProgrammingPart1
WhatisObject-OrientedProgramming?
Writingourownclass
Fields
Properties
Methods
Constructors
InstantiatinganObject
StaticKeyword
AdvancedMethodConcepts


UsingArraysandLists
Usingparamskeyword
PassingValueTypevsReferenceTypeParameters

Chapter8:Object-OrientedProgrammingPart2
Inheritance
WritingtheParentClass
WritingtheChildClass
TheMain()method

Polymorphism
GetType()andtypeof()
AbstractClassesandMethods
Interfaces
AccessModifiersRevisited

Chapter9:EnumandStruct
Enum
Struct

Chapter10:LINQ

Chapter11:FileHandling
ReadingaTextFile
WritingtoaTextFile

Project–ASimplePayrollSoftware
Overview
TheStaffClass
Fields
Properties
Constructor
Method
TheManager:StaffClass
Fields
Properties
Constructor


Method

TheAdmin:StaffClass
Fields
Property
Constructor
Method
TheFileReaderClass
ThePaySlipClass
Fields
Enum
Constructor
Methods
TheProgramClass
TheMain()Method

ThankYou

AppendixA–ProjectAnswer



Chapter1:IntroductiontoC#

WelcometoC#programmingandthankyousomuchforpickingupthis
book!
Whetheryouareaseasonedprogrammeroracompletenovice,thisbookis
writtentohelpyoulearnC#programmingfast.Topicsarecarefullyselected
togiveyouabroadexposuretoC#whilenotoverwhelmingyouwith
informationoverload.

Bytheendofthebook,youshouldhavenoproblemwritingyourownC#

programs.Infact,wewillbecodingasimplepayrollsoftwaretogetheraspart
oftheprojectattheendofthebook.Readytostart?

First,let’sanswerafewquestions:


WhatisC#?

C#,pronouncedasCSharp,isanobject-orientedprogramminglanguage
developedbyMicrosoftintheearly2000s,ledbyAndersHejlsberg.Itispart
ofthe.Netframeworkandisintendedtobeasimplegeneral-purpose
programminglanguagethatcanbeusedtodevelopdifferenttypesof
applications,includingconsole,windows,webandmobileapplications.
Likeallmodernprogramminglanguages,C#coderesemblestheEnglish
languagewhichcomputersareunabletounderstand.Therefore,C#codehas
tobeconvertedintomachinelanguageusingwhatisknownasacompiler
(refertofootnote).Thecompilerthatwe’llbeusinginthisbookisthefree
VisualStudioCommunity2015providedbyMicrosoft.


WhyLearnC#?

C#hassyntaxandfeaturesthatresembleotherprogramminglanguageslike
JavaandC++.Assuch,ifyouhaveanypriorprogrammingexperience,you
willfindlearningC#abreeze.Evenifyouaretotallynewtoprogramming,
C#isdesignedtobeeasytolearn(unlikeCorC++)andisagreatfirst


languagetolearn.

Inaddition,C#ispartofthe.Netframework.Thisframeworkincludesalarge
libraryofpre-writtencodethatprogrammerscanusewithouthavingtowrite
everythingfromscratch.Thisallowsprogrammerstorapidlydeveloptheir
applicationsinC#,makingC#theideallanguagetoworkwithifyouareona
tightschedule.

Lastly,C#isanobject-orientedprogramming(OOP)language.Objectorientedprogrammingisanapproachtoprogrammingthatbreaksa
programmingproblemintoobjectsthatinteractwitheachother.We’llbe
lookingatvariousobject-orientedprogrammingconceptsinthisbook.Once
youmasterC#,youwillbefamiliarwiththeseconcepts.Thiswillmakeit
easierforyoutomasterotherobject-orientedprogramminglanguagesin
future.

ReadytodipyourtoesintotheworldofC#programming?Let’sgetstarted.



Footnote:
TheconversionofaC#programintomachinelanguageisactuallyabitmorecomplicatedthanthis.
VisualStudioCommunitymerelyconvertsaC#programintoMIL,whichstandsforMicrosoft
IntermediateLanguage.ThisMILcodeisthenconvertedintomachinelanguagebyavirtualexecution
systemknownastheCommonLanguageRuntime.Formoreinformation,youcancheckout
Nonetheless,forourpurpose,wedonotneed
toknowtheseintricatedetailstodevelopourownC#programs.




Chapter2:GettingreadyforC#

InstallingVisualStudioCommunity

BeforewecanstartdevelopingapplicationsinC#,weneedtodownload
VisualStudioCommunity.AsmentionedinChapter1,VisualStudio
Community(VSC)isafreecomplierprovidedbyMicrosoft.

Infact,VSCismorethanjustacompiler.ItisanIntegratedDevelopment
Environment(IDE)thatincludesatexteditorforustowriteourcodeanda
debuggertohelpusidentifyprogrammingerrors.

TodownloadVSC,goto />


Clickonthe“DownloadCommunity2015”buttontodownloadthefile.Once
youhavedownloadedthefile,doubleclicktoinstallVSC.Afteryouinstall,
you’llbepromptedtorestartyourcomputer.

Onceyourestartyourcomputer,youarereadytostartcodingyourfirstC#
program.




YourFirstC#Program

Towriteourfirstprogram,let’screateafolderonourdesktopandnameit
“C#Projects”.WewillsaveallourC#projectstothisfolder.

Next,launchVSCandselectFile>New>Project….(Youmayhaveto

searchfor“VisualStudio2015”ifyoucannotfindVSC.)Thefirstprogram
thatwearegoingtowriteisaconsoleapplication.Consoleapplicationsrefer
toprogramsthathavenographicaluserinterface.

FromtheNewProjectdialogbox,select“VisualC#>Windows”(ontheleft)
andselect“ConsoleApplication”inthemainbox.

Namethisprogram“HelloWorld”andsaveitinthe“C#Projects”folder
createdearlier.Youcanusethe“Browse…”buttontobrowsetothecorrect
folder.Finally,clickOKtocreatetheproject.




YouwillbepresentedwithadefaulttemplatethatVSCcreatedforyou
automatically.

Replacethecodeinthetemplatewiththecodebelow.Notethatlinenumbers
areaddedforreferenceandarenotpartoftheactualcode.Youmaywantto
bookmarkthispageforeasyreferencelaterwhenwediscusstheprogram.
Duetothesmallscreensizesofmostmobiledevices,thecodemaylook
jumbledupifyouareviewingitonaKindle,tabletormobilephone.Ifyou
haveproblemsreadingthecode,youcantrychangingyourscreento
landscapemode.Alternatively,youcandownloadthesourcecodeforthis
sampleprogramandallothersampleprogramsinthisbookat
/>


1usingSystem;
2usingSystem.Collections.Generic;

3usingSystem.Linq;
4usingSystem.Text;
5usingSystem.Threading.Tasks;
6
7namespaceHelloWorld
8{
9
10//ASimpleProgramtodisplaythewordsHelloWorld
11
12classProgram
13{
14staticvoidMain(string[]args)
15{
16Console.WriteLine(“HelloWorld”);
17Console.Read();
18}
19}
20}


Istronglyencouragethatyoutypethecodeyourselftogetabetterfeelfor
howVSCworks.Asyoutype,youwillnoticethataboxappearsnearthe
cursorwithsomehelpmessagesoccasionally.ThatisknownasIntellisense.
Forinstance,whenyoutypeaperiod(.)aftertheword“Console”,adropdrop
listappearstoletyouknowwhatyoucantypeaftertheperiod.Thisisoneof
thefeaturesofVSCtohelpmakecodingeasierforprogrammers.

Afteryoufinishtyping,youcanexecutethisprogrambyclickingonthe
“Start”buttonatthetopmenu(refertoimagebelow).

Ifyourprogramfailstorun,VSCwillinformyouoftheerrorinthe“Output
Window”.Doubleclickingontheerrormovesthecursortowheretheerroris.
Doublecheckyourcodeagainstthecodeabovetorectifytheerrorandrun
theprogramagain.

Ifallgoeswellandyourprogramrunssuccessfully,ablackwindowwill
appearwiththewords“HelloWorld”inwhite.Thisblackwindowisknown
astheconsole.PressEntertoclosethewindow.

That’sit!Youhavesuccessfullycodedyourfirstprogram.Giveyourselfapat
ontheshoulders.



Ifyounavigatetoyour“C#Projects”foldernow,you’llfindafoldernamed
“HelloWorld”.Withinthefolder,you’llfindanother“HelloWorld”folderand
a“HelloWorld.sln”file.This.slnfileisthesolutionfile.Wheneveryouneed
toreopenaproject,thisisthefiletoopen.Ifthetexteditordoesnotdisplay
yourcodewhenyouopenthesolutionfile,simplydoubleclickonthe
“Program.cs”fileinthe“SolutionExplorer”ontheright(refertotheprevious
image)toopenit.

Theexecutablefile(.exe)ofyourcodecanbefoundintheHelloWorld>
HelloWorld>bin>Debugfolder.


BasicStructureofaC#Program

Now,letusdoaquickrun-throughofthebasicprogramthatyouhavejust
coded.


Directive

Fromline1to5,wehaveafewstatementsthatstartwiththewordusing.
Thesestatementsareknownasdirectives.Theytellthecompilerthatour
programusesacertainnamespace.

Forinstance,thefirstline

usingSystem;


tellsthecompilerthatourprogramusestheSystemnamespace.


Namespace

Anamespaceissimplyagroupingofrelatedcodeelements.Theseelements
includeclasses,interfaces,enumsandstructsetc(we’llcovereachofthese
elementsinsubsequentchapters).



C#comeswithalargeamountofpre-writtencodethatareorganisedinto
differentnamespaces.TheSystemnamespacecontainscodeformethodsthat
allowustointeractwithourusers.Weusetwoofthesemethodsinour

program-theWriteLine()andRead()methods.Theothernamespacesare
notneededinourprogram.However,sincethesenamespacesareincludedin
thedefaulttemplate,we’llleaveitinourcode.
Inadditiontothepre-writtennamespacesprovidedbyMicrosoft,wecanalso
declareourownnamespaces.

Oneadvantageofdeclaringnamespacesisthatitpreventsnamingconflicts.
Twoormorecodeelementscanhavethesamenameaslongastheybelongto
differentnamespaces.Forinstance,thecodebelowdefinestwonamespaces,
bothofwhichcontainaclassnamedMyClass.ThisisallowedinC#asthe
twoclassesbelongtodifferentnamespaces(FirstandSecond).

namespaceFirst
{
classMyClass
{
}
}


namespaceSecond
{
classMyClass
{
}
}


Inourexample,wedeclaredonenamespace-HelloWorld.

TheHelloWorldnamespacestartsonline7,withanopeningcurlybraceon
line8.Itendsonline20withaclosingcurlybrace.Curlybracesareused
extensivelyinC#toindicatethestartandendofacodeelement.Allopening


bracesinC#mustbeclosedwithacorrespondingclosingbrace.

WithintheHelloWorldnamespace,wehavetheProgramclasswhichstartson
line12andendsonline19.WithintheProgramclass,wehavetheMain()
methodthatstartsonline14andendsonline18.


TheMain()Method

TheMain()methodistheentrypointofallC#consoleapplications.
Wheneveraconsoleapplicationisstarted,theMain()methodisthefirst
methodtobecalled.

Inthisbook,wheneveryouareaskedtotryoutacertaincodesegment,you
shouldcreateanew“ConsoleApplication”andtypethegivencodesegment
intotheMain()method(betweenthecurlybraces).Youcanthenrunthe
programtotestthecode.

Noticethewords“string[]args”insidetheparenthesisofourMain()method?
ThismeanstheMain()methodcantakeinanarrayofstringsasinput.Donot
worryaboutthisforthemoment.We’llcoverthesetopicsinsubsequent
chapters.
Inourexample,theMain()methodcontainstwolinesofcode.Thefirstline

Console.WriteLine(“HelloWorld”);

displaystheline“HelloWorld”(withoutthequotes)onthescreen.

Thesecondline

Console.Read();


waitsforakeypressfromtheuserbeforeclosingthewindow.
Bothofthestatementsaboveendwithasemi-colon.Thisiscommonformost


statementsinC#.AftertheConsole.Read()statement,weendourcodewith
threeclosingbracestoclosetheearlieropeningbraces.

That’sit!There’sallthereistothissimpleprogram.


Comments

We’vecoveredquiteabitinthischapter.Youshouldnowhaveabasic
understandingofC#programmingandbereasonablycomfortablewithVSC.
Beforeweendthischapter,there’sonemorethingtolearn-comments.
Ifyoureferbacktoour“HelloWorld”exampleandlookatline10,you
shouldnoticethatthislinestartswithtwoforwardslashes(//).

//ASimpleProgramtodisplaythewordsHelloWorld

Thislineisactuallynotpartoftheprogram.Itisacommentthatwewriteto
makeourcodemorereadableforotherprogrammers.Commentsareignored
bythecompiler.

Toaddcommentstoourprogram,wetypetwoforwardslashes(//)infront
ofeachlineofcommentlikethis

//Thisisacomment
//Thisisanothercomment
//Thisisyetanothercomment


Alternatively,wecanalsouse/*…*/formultilinecommentslikethis

/*Thisisacomment
Thisisalsoacomment
Thisisyetanothercomment
*/




Commentscanalsobeplacedafterastatement,likethis:

Console.Read();//readsthenextcharacter




Chapter3:TheWorldofVariablesandOperators

NowthatyouarefamiliarwithVSCandhavewrittenyourfirstprogram,let’s
getdowntotherealstuff.Inthischapter,you’lllearnallaboutvariablesand
operators.Specifically,you’lllearnwhatvariablesareandhowtoname,
declareandinitializethem.You’llalsolearnaboutthecommonoperations
thatwecanperformonthem.


Whatarevariables?

Variablesarenamesgiventodatathatweneedtostoreandmanipulateinour
programs.Forinstance,supposeyourprogramneedstostoretheageofa
user.Todothat,wecannamethisdatauserAgeanddeclarethevariable
userAgeusingthefollowingstatement:

intuserAge;


Thedeclarationstatementfirststatesthedatatypeofthevariable,followedby
itsname.Thedatatypeofavariablereferstothetypeofdatathatthevariable
willstore(suchaswhetherit’sanumberorapieceoftext).Inourexample,
thedatatypeisint,whichreferstointegers.Thenameofourvariableis
userAge.

AfteryoudeclarethevariableuserAge,yourprogramwillallocateacertain
areaofyourcomputer’sstoragespacetostorethisdata.Youcanthenaccess
andmodifythisdatabyreferringtoitbyitsname,userAge.


DataTypesinC#

ThereareanumberofcommonlyuseddatatypesinC#.


int



intstandsforinteger(i.e.numberswithnodecimalorfractionalparts)and

holdsnumbersfrom-2,147,483,648to2,147,483,647.Examplesinclude15,
407,-908,6150etc.


byte

bytealsoreferstointegralnumbers,buthasanarrowerrangefrom0to255.


Mostofthetime,weuseintinsteadofbyteforintegralnumbers.However,
ifyouareprogrammingforamachinethathaslimitedmemoryspace,you
shouldusebyteifyouarecertainthevalueofthevariablewillnotexceedthe
0to255range.

Forinstance,ifyouneedtostoretheageofauser,youcanusethebytedata
typeasitisunlikelythattheuser’sagewilleverexceed255yearsold.


float

floatreferstofloatingpointnumbers,whicharenumberswithdecimal

placessuchas12.43,5.2and-9.12.

floatcanstorenumbersfrom-3.4x1038to+3.4x1038.Ituses8bytesof

storageandhasaprecisionofapproximately7digits.Thismeansthatifyou
usefloattostoreanumberlike1.23456789(10digits),thenumberwillbe
roundedoffto1.234568(7digits).


double

doubleisalsoafloatingpointnumber,butcanstoreamuchwiderrangeof

numbers.Itcanstorenumbersfrom(+/-)5.0x10-324to(+/-)1.7x10308and
hasaprecisionofabout15to16digits.

doubleisthedefaultfloatingpointdatatypeinC#.Inotherwords,ifyou
writeanumberlike2.34,C#treatsitasadoublebydefault.




decimal

decimalstoresadecimalnumberbuthasasmallerrangethanfloatand
double.However,ithasamuchgreaterprecisionofapproximately28-29

digits.

Ifyourprogramrequiresahighdegreeofprecisionwhenstoringnonintegral
numbers,youshoulduseadecimaldatatype.Anexampleiswhenyouare
writingafinancialapplicationwhereprecisionisveryimportant.


char

charstandsforcharacterandisusedtostoresingleUnicodecharacterssuch

as‘A’,‘%’,‘@’and‘p’etc.


bool

boolstandsforbooleanandcanonlyholdtwovalues:trueandfalse.Itis

commonlyusedincontrolflowstatements.We’llcovercontrolflow
statementsinChapter6.


NamingaVariable

AvariablenameinC#canonlycontainletters,numbersorunderscores(_).
However,thefirstcharactercannotbeanumber.Hence,youcannameyour
variablesuserName,user_nameoruserName2butnot2userName.

Inaddition,therearesomereservedwordsthatyoucannotuseasavariable
namebecausetheyalreadyhavepreassignedmeaningsinC#.Thesereserved
wordsincludewordslikeConsole,if,whileetc.We’lllearnabouteachof

theminsubsequentchapters.



Finally,variablenamesarecasesensitive.usernameisnotthesameas
userName.

TherearetwoconventionswhennamingavariableinC#.Wecaneitheruse
thecamelcasenotationoruseunderscores.Camelcasingisthepracticeof
writingcompoundwordswithmixedcasing,capitalisingthefirstletterof
eachwordexceptthefirstword(e.g.thisIsAVariableName).Thisisthe
conventionthatwe’llbeusingintherestofthebook.Alternatively,another
commonpracticeistouseunderscores(_)toseparatethewords.Ifyou
prefer,youcannameyourvariableslikethis:this_is_a_variable_name.


InitializingaVariable

Everytimeyoudeclareanewvariable,youneedtogiveitaninitialvalue.
Thisisknownasinitializingthevariable.Youcanchangethevalueofthe
variableinyourprogramlater.

Therearetwowaystoinitializeavariable.Youcaninitializeitatthepointof
declarationorinitializeitinaseparatestatement.
Theexamplesbelowshowhowyoucaninitializeavariableatthepointof
declaration:

Example1

Theseexamplesshowhowyoucaninitializebyteandintvariables.

byteuserAge=20;
intnumberOfEmployees=510;


Asbyteandintarefordatawithnodecimalplaces,youwillgetanerrorif
youwritesomethinglike

byteuserAge2=20.0;




20.0isnotthesameas20inC#.

Example2

Thenextexamplesshowhowyoucaninitializedouble,floatanddecimal
variableswithintegralvalues.Althoughthesedatatypesarefornumberswith
decimalparts,wecanalsousethemtostoreintegralvaluesasshownbelow.

doubleintNumberOfHours=5120;
floatintHourlyRate=60;
decimalintIncome=25399;


Example3

Theexamplesbelowshowhowyoucaninitializedouble,floatanddecimal
variableswithnonintegers.

doublenumberOfHours=5120.5;
floathourlyRate=60.5f;
decimalincome=25399.65m;


Asmentionedpreviously,thedefaultdatatypeforanumberwithdecimal
placesisdouble.

Hence,intheexamplesabove,whenyouinitializehourlyRate,youneedto
add‘f’asasuffixafter60.5toexplicitlytellthecompliertochange60.5toa
float.
Similarly,whenyouinitializeincome,youneedtoadd‘m’asasuffixto
change25399.65intoadecimaldatatype.

Example4

Achardatatypecanonlycontainasinglecharacter.Whenweinitializea