building applicaons in c#cdn.cs50.net/2011/fall/seminars/c_sharp/c_sharp.pdf · • allows...

BuildingApplica-onsinC#

MikeTeodorescu’11Microso9

Hello

•  CS50TF‘09,‘10•  CSconcentratorclassof2011•  WorkedonWindowsHomeandSmallBusinessServer2011asaninterninRedmond,WA

•  NowengineerintheApplica-onVirtualiza-onteamattheMicroso9NewEnglandResearchandDevelopmentCenter(NERD)

Microso9NERD

•  Teams:– Applica-onVirtualiza-on– Microso9Research–  SharepointWorkspace2010– Office365– Microso9Lync–  Interac-veEntertainmentBusiness– Microso9Adver-sing– Microso9‐NovellInteroperabilityLab

•  Address:1MemorialDriveinCambridge•  h\p://microso9cambridge.com

•  Allowsapplica-onstoruninseparatevirtualenvironments,elimina-ngconflictswithotherapplica-onsorwithdifferentversionsofthesameapplica-on.

•  Previouslyincompa-bleappscanberunsimultaneously

•  Fullyfunc-onalWindowsappsarestreamedondemandtousers’desktops

•  Weworkonverylargescalesystems•  Moreath\p://microso9cambridge.com/Teams/Applica-onVirtualiza-on/tabid/83/Default.aspx

TOC1.  IntrotoC#2.  HelloWorld3.  Object‐Orientedconcepts4.  Collec-ons5.  ControlFlow6.  FileI/O7.  StringsandREGEX8.  XMLandLINQQueries9.  Excep-onHandling10. Debugging

IntrotoC#•  Object‐orientedprogramminglanguage•  Type‐safetyguaranteed– cannotstoredataofonetypeinaloca-oncorrespondingtoadifferenttype

– cannothaveunini-alizedvariables•  Garbagecollec-on–automa-cmemorymanagement(noneedtoworryaboutfreeingmemoryyouallocated)

•  Built‐indatastructuresthathandletheirownsizing•  Excep-onhandlingallowsdetec-onandrecoveryfromerrorsduringexecu-onofyourcode

IntrotoC#(2)•  CodeissandboxedintoaVirtualExecu-onSystemwhichensuressafecodeexecu-onandmemorymanagement

•  C#comeswiththe.NETFrameworkClassLibrary,whichmeansitispackedwithlibrariesthatsimplifymanycommontasksthatyouwouldotherwisehavetocode:–  XMLandstringparsing– webprogramming–  datastructures–  scalablenetworksandserverprogramming–  databasemanagement– GUIprogramming,andothers…

•  Parallelprogrammingmadeeasy(ParallelCompu-ngPla=orm–takescareofthelowerlevelcodingforyou)

IntrotoC#(3)•  Standardtypesarebuilt‐in•  YoucancreateyourcustomtypesthroughOO

•  C#enablescomponent‐orientedprogramming,whichmeansyoucancreateself‐containedunitsoffunc-onalitythatcancommunicate

•  Yourcodeisalivingecosystem–extensibleandeasytomaintain.

•  Thegoalistoallowyoutospendmore-meontheconceptsandlessonlower‐leveldetails.Itenablesyoutothinkmoreaboutyoursolu-onandtheabstractmodelbehindit.

DevelopmentEnvironment•  SomebenefitsofusingVisualStudio2010:– Mul-tudeoflanguagesyoucanuse(VisualC#,VisualC++,VB)–the.NETlanguagesalluseacommontypesystem

– Auto‐Complete– Auto‐formapng

– Cross‐plaqormdevelopment– Mul-tudeofcodetemplatesandstubs– Debuggingmadeeasy

–  IntegratedGUIdesigntools–  IntegratedTes-ngtools

DevelopmentEnvironment(2)•  Sourcecontrol•  Candevelopanythingfromaconsoleappto:–  clouddevelopment,– GUIapps,– webservers,– webapps,–  tes-ngframeworks,– Windows8apps,– WindowsPhoneapps,– Officeadd‐ins,–  toverylargecollabora-veprojects

Basics

•  Usingstatement•  Referencing•  Namespace‐seehierarchydenotedusing.–  System–  System.Collec-ons–  System.Collec-ons.Generic

•  Class•  Method•  DEMO

ObjectOriented

•  Programmingwithclassesmakesformoreextensiblecode(allowingyouforinstancetodefineyourowntypesandcontrolwhatisaccessible

•  Encapsula-on=hideinternalimplementa-ondetailsofaclass(datahiding,thisisprivate)

•  Abstrac-on=publicinterfaceofaclass,theexternaldetailssuchasac-onsthattheclasscanperform(thisisvisibletoeveryone)

OO(2)

•  Tocreateanobjectofthetypedefinedinaclass,weneedtoinstan-atethatclass.Tobeabletodoso,theclassmustdefineaconstructor:

myClassfoo=newmyClass();•  Constructorscanbeoverloaded–wecancreateseveralmethodswiththesamenamebutdifferentparameters(thusdifferentsignatures)

OO(3)

•  Modifiers– private–onlyaccessibleinsidetheclass– public–accessiblebyeveryone– sta-c–dataandmethodsthatcanbeaccessedwithoutcrea-nganinstanceoftheclass

– const–forconstants•  Scope:Namespaces,classes,andmethods

OO(4)

•  Amethodinaclassisafunc-on–it’sbasicallyanac-onthatanobjectdefinedbytheclasscantake

•  Apropertyinaclassisadataitemwhosereadandwriteaccessisdefinedbyyou(requireagetandaset:

public class Student {

//privately set private string _name; public string Name { //public read get return _name; }

}

OO(5)

•  Inheritance:aclasscaninheritallcharacteris-csandac-onsfromaparentclass

•  Thechildclasscanhaveitsownprivatedata,addedmethodsthatarenotfoundintheparent,orredefinethebehaviorofinheritedmethods

•  Aclasscanonlyinheritfromoneparent

•  DEMO

Arrays// Single-dimensional int[] array1 = new int[10];

// Declare and set values for a single-dimensional array int[] array2 = new int[] { 1, 2, 3 };

// OR int[] array2 = { 1, 2, 3 };

// Declare a 2D array int[,] twoDimensionalArray1 = new int[2,1];

// Declare and set 2D array int[,] twoDimensionalArray2 = { { 1 }, { 2 } };

ArrayIni-aliza-onandIndexing

Class Program

{ static void Main()

{ int[] array = new int[10];

for(int i=0; i < array.Length; i++)

array[i] = i*i; }

}

ArrayClassSta-cMethods

•  void Clear(array, index, len) – setsarangetonull,orzero,orfalse,dependingontheelementtypeofthearray

•  int BinarySearch(array, value, comparer) –returnseithertheindexofthesearchedvalue,oranega-venumberifthevalueisnotfound

•  void ForEach(action) – performs the action on each element of the array

GenericCollec-ons

•  Workwithbuilt‐inanddeveloper‐definedtypes(thus“Generic”–alltypesyoudefineinheritfromobject)

•  Immediatebenefits:typesafety•  AredefinedintheSystem.Collec-ons.Genericnamespace

•  Providealargevariety,readyforyouruse:Lists,Dic-onaries,SortedLists,LinkedLists,SortedDic-onaries,Sets,Stacks,Queues,andmore…

List<T>

•  Unlikeanarray,aListdynamicallysizesasneeded

•  Ifyouneedsequen-alaccesstoelements,useaLinkedList<T>

•  Listssupportaddinganelementorarangeofelementsattheendofthelist(AddandAddRange)

Dic-onary<Tkey,Tvalue>

•  Usefulmethods:– ContainsKey,– ContainsValue,– Remove(removesthevalueassociatedwiththepassedkey)

– Clear– Add(willthrowanexcep-onifkeyalreadyexistsmustcheckifthedictcontainsthekeyyoutrytoadd)

– TryGetValue(getsthevalueassociatedwiththekeyyou’repassingtoit)

MoreAdvanced

•  Forfuturedevelopmentinterests:

Thread‐safecollec-ons(ConcurrentDic-onary)

ReadilyusableinSystem.Threading.Tasks.Parallel

(generallythetaskparallellibrarymakesmul-threadedprogrammingprojectssimplertodevelopbytakingcareofsomelowerleveldetails)

ControlFlow

•  If/else,switch,for,while,dowhile,arethesame

•  FOREACHstatement–neatsincewehavedatastructuresthathaveanenumeratordefinedonthem(suchaslists,dicts,etc)foreach(varkeyvalueindic-onary){…}DEMOfordatastructuresbundledwithStringsdemo

StringsandREGEX

•  Built‐intypescharandstring•  EmptystringisString.Emptyor“”

•  Unassignedstringisanull•  Caneasilycreatestringsfromotherobjectsbycalling.ToString()

•  String.Compare(string,string)

•  String.Concat(string,string)•  String.Split(tokenChar)

REGEX(1)•  Regularexpressionsenableyoutoperformpa\ernmatching

•  RequireusingSystem.Text.RegularExpression

•  Steps:– Defineapa\ernyouwishtomatch(thisisoftypestring)

–  Regexexpression=newRegex(pa\ern);–  expression.IsMatch(stringYouWishToMatch);

OR– MatchCollec-onlist=expression.Matches(stringYouWishToMatch);

(thisisthesetofallmatchesbyapplyingtheregexrepeatedly)

REGEX(2)•  Pa\erns:

?matchesprecedingelement0or1+matchesprecedingelement1ormore-mes*Matchesprecedingelement0ormore\dmatchesdecimaldigit(equivalentto[0‐9])\wmatchesanalphanumericchar(equivto[a‐zA‐Z_0‐9]{p}matchesprecedingelementexactlyp-mes{p,q}matchesprecedingelementatleastpbutlessthanq-mes.matchesanycharacterexcept\n[]matchesthecharacterwithinthebrackets[^]NOT(e.g,[^0‐9]matcheseverythingnot0thru9)\smatchesaspace

REGEX(3)•  Groups:youcandesignategroupswithinyourpa\ernusing()

•  Examplepa\erns:

[0‐9]*

\d{3}\w+

([a‐zA‐Z^0‐9]){3,5}(\d*(\w+))

(\d*(\w+)?)+

FILEI/O

•  CoveredinStringsREGEXDEMO:– Pathbuilder– Readingfromastream– Wri-ngtoastream– Alsofeatured:star-ngachildprocessandclosingthatprocess

XMLandLINQ•  Thissec-onwillshowyouhoweasyitistocreateanXMLparserwithjustafewlinesofcode

•  LINQisthequeryingmechanism(canbeusedforalsofordatabases)

•  Wewillneed:– usingSystem.Xml.Linq

– usingSystem.Xml– usingSystem.Collec-ons.Generic

XMLExamples•  AnXMLelementcorrespondstotheXElementtype:

<courses> <course Title = “CS50” Location = /> <course Title = “CS121” Location =

“Maxwell Dworkin” /> … </courses>

•  Herecourseisanelement,TitleandLoca-onarea\ributes.WecanstorethemusingtheXElementtype;moreoverwecannavigatea\ributesstoringthemusingtypeXA\ribute.

XMLExamples<students> <student> <name>Barney</name> <class>2013</class> <house>Currier</house> </student> … </students>

SepngXMLelementsXElement xmlDocument =

new XElement(“students”, new XElement(“student”, new XElement(“name”), new XElement(“class”), new XElement(“house”) ) );

•  Nowwehavetosetthevaluesoftheelementswejustcreated: XElement student=xmlDocument.Element(“student”); student.SetElementValue(“name”, “Mike”); //you can see that an XElement stores a //key-value pair – great for storing in a dict

QueryingXML•  YouneedtofirstsettherootelementoftheXML:Root=XElement.Load(“C:\Foo\bar.xml”);

•  Toaccessallelementsundertherootnode:Root.Elements()

•  Topickthevalueofthefirstelement:Root.Elements().First().FirstA\ribute.Value

QueryingXML

•  LINQqueryisverysimilartotheSQLqueryyou’refamiliarwith:

FROMelementinRoot.Elements()

SELECTelement

WHERE(…)

No-cethattheFROMactslikeaforeach

VS2010andXMLsinProjects

•  ItisnotsufficienttoaddtheXMLfiletoyourprojectsolu-on

•  YoumustalsosetintheXMLfile’sProper-estabthe“CopytoOutputDirectory”to“CopyAlways”

•  ThisdoesnotapplyifyourXMLisfromaURL(thenyoudon’tincludeacopyofit,youjustpasstheURLpathtotheLoadmethod).

Excep-ons(1)

•  Excep-onsserveasameanstoreportfailures,classify,andhandlethem

•  Excep-onsencapsulatealltheinforma-onaboutanerrorinasingleclass‐touseexcep-onsaddausingstatementforusingSystem.Excep-on;

•  Allexcep-onsderivefromtheSystem.Excep-onclass

Excep-ons(2)

•  TheSystem.Excep-onclassprovidesseveralusefulproper-esfordebugging:– Message– StackTrace– HelpLink(op-onalURL)– Data(thisisadic-onary)–  InnerExcep-on(ifanexcep-oniswrappedintoadifferenttypeofexcep-on)

•  Howto“throw”anexcep-on:thrownewSystem.Excep-on();

Excep-ons(3)

•  Standardexcep-ontypes:– ArgumentExcep-on– ArgumentNullExcep-on– DivideByZeroExcep-on– NullReferenceExcep-on–  InvalidOpera-onExcep-on–  IndexOutOfRangeExcep-on– OutOfMemoryExcep-on– StackOverFlowExcep-on– SystemExcep-on

Excep-ons(4)–HandlingLogic•  Try‐Catchblock:youexecutecodeintheTryblockwhichmaythrowanexcep-onofaspecifictypewhichyouthenhandleinthecatchblock:try { int foo = 3/0;

} catch(DivideByZeroException e) { Console.Writeline(“Why did you divide by

zero?”); }

Excep-ons(5)–HandlingLogic•  Try‐Catchblock:youmayhavemul-plecatchblocksfordifferenttypesofexcep-onssuchthatdependingontheexcep-onyouexecuteadifferentblockofcode.

•  Example:catch(SystemException e1) { …} catch(ArgumentException e2) {…} catch(InvalidOperationException e3) {…}

Excep-ons(6)–HandlingLogic

•  Catchblockscanswallowerrors–ifyoujustloganerrormessageinyourcatchblockanddonothandletherootcauseoftheerror,thenyouwillfallintothebaddesignprac-cecalled“swallowinganexcep-on”.

•  Ifyourapplica-onthrowsanexcep-onthatisunhandledbyacatchblockwillresultinanapplica-oncrash.

Excep-ons(7)–HandlingLogic

•  Try‐Finally–thefinallyblockofcodeexecutesregardlessofwhetherornotanexcep-onwasthrowninthetryblock;thefinallyblockexecutesimmediatelya9erthetryblock

•  Try‐Catch‐Finally‐mayhavemul-plecatchblocks,asbefore,butalwaysasinglefinallyblock.

•  DEMO

MoreAdvanced

•  IFyouenterasitua-oninwhichitisunsafetocon-nue(securityrisksforexample,memorycorrup-on,etc.),insteadofusinganexcep-onuseSystem.Environment.FailFast.

•  FailFastimmediatelyterminatestheapplica-on

•  Suchtermina-onsareshownintheeventlogfortheapplica-on(intheWindowseventlog)

1.  IntrotoC#2.  BasicSyntax3.  HelloWorld4.  Object‐Orientedconcepts5.  Datastructures6.  ControlFlow7.  FileI/O8.  REGEX9.  Excep-onHandling10. Debugging[DEMO]

Morereferences

•  h\p://msdn.microso9.com•  Alwaysgoodtouse:F12allowsyoutotraveltothedefini-onofatypethatbelongstoareferencedlibrary

Thanks!

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