.NET Framework and C#: Overview, Namespaces, Classes, and Windows Forms

1. MicrosoftVisualStudio 2005/2008 andthe.NETFramework (C)RichardR.Eckert TheMicrosoft.NETFramework •TheCommonLanguageRuntime •CommonLanguageSpecification –ProgrammingLanguages •C#,VisualBasic,C++,lotsofothers •ManagedModules(Assemblies) •MSIL •The.NETFrameworkClassLibrary (C)RichardR.Eckert

2. .NETArchitecture (C)RichardR.Eckert Compilationinthe.NET Framework Common Language Runtime

3. Namespace •Acollectionofrelatedclassesandtheirmethods •FCLiscomposedofnamespaces •NamespacesarestoredinDLLassemblyfiles •.NETapplicationsmusthave“references”tothese DLLssothattheircodecanbelinkedin •AlsoshouldbeincludedinaC#programwiththeusing declaration –e.g.usingSystem.Windows.Forms; –Ifleftout,youmustgivethefullyqualifiednameofanyclassmethodorpropertyyouuse,e.g. System.Windows.Forms.MessageBox.Show(…); •SomethinglikeapackageinJava (C)RichardR.Eckert SomeImportant.NetNamespaces •SystemCoredata/auxiliaryclasses •System.CollectionsResizablearrays+othercontainers •System.DataADO.NETdatabaseaccessclasses •System.DrawingGraphicalOutputclasses(GDI+) •System.IOClassesforfile/streamI/O •System.NetClassestowrapnetworkprotocols •System.ThreadingClassestocreate/managethreads •System.WebHTTPsupportclasses •System.Web.ServicesClassesforwritingwebservices •System.Web.UICoreclassesusedbyASP.NET •System.Windows.FormsClassesforWindowsGUIapps •Seeonlinehelpon‘ClassLibrary’ (C)RichardR.Eckert

4. C# •Anewcomponent&objectorientedlanguage -Emphasisontheuseofclasses •PowerofC++andeaseofuseofVisualBasic •CombinesthebestaspectsofC++andJava -ConceptuallysimplerandmoreclearthanC++ •Muchsmallercodefilesandexecutables -MorestructuredthanVisualBasic -MorepowerfulthanJava -Manygreatnewconstructs •SyntaxverysimilartoC/C++ -Noheaderfiles •Managedpointersonly -"Almostnopointers"�"almostnobugs" (C)RichardR.Eckert C#Classes -“Fields”:Datamembers(likeC++variables) -“Methods”:Codemembers(likeC++functions) -“Properties”:In-betweenmembersthatexposedata •Totheuserprogramtheylooklikedatafields •Withintheclasstheylooklikecodemethods •Oftentheyprovidecontrolledaccesstoprivatedatafields -Validitycheckscanbeperformed -Valuescanbeobtainedorchangedaftervaliditychecks »PropertiesuseAccessormethodsget()andset() »get()toretrievethevalueofadatafield…returndata-field; »set()tochangethevalueofadatafield…data-field=value; -OtherclassesusePropertiesjustlikedatafields -"Events":Definethenotificationsaclassiscapableoffiringinresponsetouseractions (C)RichardR.Eckert •Cancontain:

5. Example:Squareclass publicclassSquare { privateintside_length=1;//AField publicintSide_length//AProperty { get{returnside_length;}//“return”:specifiesvaluegoingout set { if(value>0) side_length=value;//“value”:specifiesvaluethatcameIn else throw(newArgumentOutOfRangeException()); } } publicintarea()//AMethod { return(side_length*side_length); } publicSquare(intside)//TheConstructormethod { side_length=side; }(C)RichardR.Eckert } InstantiatingandUsingtheSquareClass Squaresq=newSquare(10);//ConstructaSquareobjectcalledsq //ofside_length=10 //Instantiatestheobjectandinvokes //theclassconstructor intx=sq.Side_length;//Retrieveobject’sSide_LengthProperty sq.Side_length=15;//Changeobject’sSide_lengthProperty inta=sq.area();//Defineanintegervariableaanduse //theclassarea()methodtocompute //theareaofthesquare MessageBox.Show(“Area=“+a.ToString()); //DisplayresultinaMessageBox //NoteuseofToString()method //toconvertanintegertoastring. //Show()isastaticmethodofMessageBox //class (C)RichardR.Eckert

6. WindowsForms •AWindowsForm:In.NETit’sjustawindow •Formsdependonclassesinthenamespace‘System.Windows.Forms’ •Formclassisin‘System.Windows.Forms’: -TheheartofeveryWindowsFormsapplicationisaclassderivedfromForm •Aninstanceofthisderivedclassrepresentstheapplication’smainwindow •InheritsmanypropertiesandmethodsfromFormthatdeterminethelookandbehaviorofthewindow -E.g.,Textpropertytochangethewindow’scaption •Application:Anotherimportantclassfrom‘System.Windows.Forms' -ItsstaticmethodRun(…)drivestheWindowsFormapplication •ArgumentistheFormtoberun -Invokedintheprogram’sentrypointfunction:Main() -Causestheprogramtocreatetheformpassedtoitandenterthemessageloop •Form’sconstructorwillrun(typicallycodetosetinitialwindowproperties) -TheformpassedtoRun()hascodetopostaQUITmessagewhenformisclosed -ReturnstoMain()whendoneandprogramterminatesproperly (C)RichardR.Eckert ASimpleWindowsFormAppinC#-- HelloWorld usingSystem.Windows.Forms;//thenamespacecontaining //theFormclass publicclassHelloWorld:System.Windows.Forms.Form {//ourclassisderivedfromForm publicHelloWorld()//ourclassconstructor { this.Text="HelloWorld";//Setthisform’sTextProperty } staticvoidMain()//Application’sentrypoint { Application.Run(newHelloWorld());//Runourform } } (C)RichardR.Eckert

7. CompilingaC#Applicationfromthe CommandLine •StartaCommandWindowwiththeproperpathstothecompiler/linkerset –Easiestway:FromTaskBar: •‘Start’|‘AllPrograms’|‘MicrosoftVisualStudio2008|‘VisualStudio Tools’|‘VisualStudio2008CommandPrompt’ •StartstheDOSBoxCommandWindow –Navigatetothedirectorycontainingthesourcecodefile(s) –FromthecommandpromptInvoketheC#compilerandlinker –Forexample,tobuildanexecutablefromtheC#sourcefile myprog.cs,typeoneofthefollowing: cscmyprog.cs(easiestway,createsaconsoleapp) csc/target:exemyprog.cs(alsocreatesaconsoleapplication) csc/t:winexemyprog.cs(createsaWindowsexecutable) csc/t:winexe/r:System.dll,System.Windows.Forms.dllmyprog.cs (toprovideaccesstoneeded.NETDLLs) (C)RichardR.Eckert UsingVisualStudiotoDevelopa SimpleC#Application“Manually” •StartVisualStudioasusual •‘File’|‘New’|‘Project’|‘VisualC#’|‘Windows’|‘Empty Project’ •Tocreatetheprogram –‘Project’|‘AddNewItem’ •VisualStudioinstalledtemplates:‘C#CodeFile’ –Thiswillbringupthecodeeditor –TypeinorcopyandpastetheC#sourcecode •Butyoumustalsoprovideaccesstosomeadditional.NETCommonLanguageRuntimeDLLs •Dothisbyadding‘References’: –‘Project’|‘AddReference’…‘.NET’tab –Select:SystemandSystem.Windows.Forms •Buildprojectasusual(‘Build’|‘BuildSolution’) (C)RichardR.Eckert

8. UsingVisualStudio’sDesignertoDevelopa SimpleC#Application •‘File’|‘New’|‘Project’|‘VisualC#’|‘Windows’|‘Windows FormsApplication’ –Givesa“designerview”oftheWindowsFormtheprojectwillcreate –Alsocreatesskeletoncodeinthree.csfiles,2classes •2Partialclasses:Form1.Designer.cs&Form1.cs+Programclass •Rightclickonform&select‘ViewCode’toseeForm1.cs •Notehowit’sbrokenupinto‘Regions’(+and-boxesontheleft) •Thesecanbeexpandedandcontracted –ToseecodegeneratedbytheVisualStudiodesigner: •InSolutionExplorer,expandForm1.cs&doubleclickon Form1.Designer.cs •Expandthe‘WindowsFormDesignergeneratedcode’Region (C)RichardR.Eckert •StartVisualStudioasusual WhereisMain()? -ExpandtheProgramclass •ThatiswhereMain()is •ItrunstheFormjustasinourmanualcode (C)RichardR.Eckert

9. ChangingFormProperties •InForm1.Designer.cs,notetheForm’spropertiesthathavebeenpreset –Changecodesothe‘Text’propertyis“ThisisaTest” •ReactivatetheDesignerViewbyclickingonthe‘Form1.cs [design]’tab –Notehowthecaptionoftheformhaschanged •Lookatthe‘Properties’window •Findthe‘Text’PropertyandchangeitbyTyping‘HelloWorld’ –ActivateForm1.Designer.csandnotehowcodehaschanged •InDesignerViewresizetheform(dragitscorners) –notehowtheClientSizepropertychangesinForm1.Designer.cscode •ChangetheBackgroundColorinthePropertiesBoxtored: –Clickon‘BackColor’|downarrow|“custom”tab|redcolorbox –GobacktoForm1.Designer.csandnotechangesincode •Buildandruntheapplication (C)RichardR.Eckert .NETManagedModules(PEAssemblies) •TheresultofbuildingaprogramwithanyofthecompilerscapableofgeneratingMSIL:VC++,C#,VB,others –AlsoILASM(IntermediateLanguageAssembler) –Assembliesaredeploymentunitsof.NETappsstoredas.EXEfiles –‘PortableExecutables’(PEs)toberunbytheCLR •Assemblystructure(contents) –Metadatafullydescribingthecompleteassemblyanditsexternaldependencies •Meanseverymanagedmoduleis“selfdescribing” •Oneofthekeystolanguageinteroperability –Typemetadatadescribingexportedtypesandmethods –MSILcode –Resources •Themanifest Akindorroadmaptotheassembly’scontents Alsocontainspermissionsneededtoruntheassembly •CanexamineAssemblieswithatoolcalledILDASM (C)RichardR.Eckert

10. TheILDASMDisassembler •Usedtoexamineanassembly’smetadataandcode •StartaCommandWindowwithproperpathto ILDASMset –Easiestway:FromTaskBar: •‘Start’|‘AllPrograms’|‘MicrosoftVisualStudio.NET’|‘Visual Studio.NETTools’| •StartstheDOSBoxCommandWindow –Navigatetothedirectorycontainingtheassembly(.exe) –InvokeILDASM •e.g.,forHelloWorldprogram: ILDASMHelloWorld.exe •Displaysawindowshowingtheassembly’sManifestandtheclassesintheassembly (C)RichardR.Eckert ASessionwithILDASM •DoubleClickon‘Manifest’ –Listofassembliesthatmoduledependson –Assemblyname –Modulesthatmakeuptheassembly •BecauseHelloWorldisasingle-fileassembly,thereisonlyone •ExpandHelloWorldclass –Classcontainstwomethods: •Aconstructor(.ctor) •Main(‘S’meansit’sastaticmethod) –ExpandMain •.entrypointisadirectiveindicatingit’swhereexecutionstarts •CodeinstantiatesaHelloWorldobjectandcallsApplication.Runfortheform –Expand.ctor •CallsparentForm’sconstructor •Puts“HelloWorld”stringonstackandcallsset_Text(…)tosettheform’sTextproperty (C)RichardR.Eckert

11. Events,Delegates,andHandlers –Events:Resultsofuseractions –Butin.NETeventsarealso“classnotifications” –Classesdefineandpublishasetofeventsthatotherclassescansubscribeto •Whenanobjectchangesitsstate(theeventoccurs),allotherobjectsthatsubscribetotheeventarenotified –Eventsareprocessedbyeventhandlermethods –Theargumentstoaneventhandlermustmatchthoseofafunctionprototypedefinitioncalledadelegate: •Amethodtowhomeventhandlingisdelegated –Amanagedpointertoafunction •Atype-safewrapperaroundaneventhandlercallbackfunction –Handlermustuseparametersspecifiedindelegatearguments •“Attaches”thehandlerfunctiontotheevent •Permitsanynumberofhandlermethodsforagivenevent (C)RichardR.Eckert (C)RichardR.Eckert

12. (C)RichardR.Eckert (C)RichardR.Eckert

13. (C)RichardR.Eckert Events,Delegates,Handlers (C)RichardR.Eckert

14. AnExample–HandlingaPaintEvent •FormclasshasaPainteventtonotifyofwindowexposures •ThedelegateisPaintEventHandler,definedas: publicdelegatevoidPaintEventHandler(objectobjSender,PaintEventArgspea); -Firstargument:sender"object"(whereeventocurred) -Secondargument"PaintEventArgs":provideseventdata •Aclasswithproperties‘Graphics’and‘ClipRectangle’ -‘Graphics’property:containsaninstantiationofthe Graphicsclass(GDI+) »Theclassisusedtodrawonaform(likeaDevice Context) -ClipRectangle:Specifiestheareaofthewindowthatneedstoberedrawn •AnyPainthandlermethodmusthavethesearguments •AndthePainthandlermustbe"attached"tothePainteventofthe Formclass(i.e.,delegatedtothehandler) DefiningthePaintEventHanderandAttaching ittotheEvent •Definingtheform’sPainteventhandlermethod: privatevoidMyPaintHandler(objectobjsender,PaintEventArgspea) { //eventhandlingcodegoeshere }; •Attachingthehandlertotheform’sEvent (delegatingittotheeventhandler): form.Paint+=newPaintEventHandler(MyPaintHandler); – FromnowonMyPaintHandler(-,-)willbecalledanytimethePainteventoccurs •Ahandlercanalsobe“detached”fromanevent: object.event-=newdelegate(method); (C)RichardR.Eckert

15. DrawingTextinResponsetoaPaintEvent •System.Drawingnamespacecontainsmanyclassesandstructuresfordrawingonawindow •Someofthem: –Bitmap,Brush,Brushes,Color,Font,Graphics,Icon,Image,Pen,Pens,Point,Rectangle,Size •GraphicsClass –RepresentsaGDI+drawingsurface •Likeadevicecontext –Containsmanygraphicsdrawingmethods •SeeHelpon‘Graphicsclass’|‘allmembers’ –Obtainingagraphicsobject: •InPainteventhandler,usesecondargument: –PaintEventArgspeaprovidesaGraphicsobject –Getitwithfollowingcode:Graphicsg=pea.Graphics (C)RichardR.Eckert UsingDrawString()toDrawText •GraphicsDrawString()methodhaslotsofoverloads •Simplest: DrawString(stringstr,Fontfont,Brushbrush,floatx,floaty); –stringclass:analiasforSystem.String •Definesacharacterstring •Alsohasmanymethodstomanipulateastring –Fontclass:givesaWindowsFormprogramaccesstomanyfontswithscalablesizes •AFormhasadefaultFont:It’soneoftheForm’sproperties •OryoucaninstantiateanewFontobject:Lotsofpossibilities(we’llseelater) –BrushorBrushesclass:color/styleofcharacters •Lotsofdifferentstaticcolorproperties,e.g. Brushes.Black,Brushes.Red •OrwecancreateoneofaspecifiedColor Brushbr=newSolidBrush(Color.FromArgb(r,g,b)); Brushbr=newSolidBrush(Color.Red); –Colorstructurehasmanystaticmethodsandproperties –x,y:Locationtodrawstringonwindowclientarea (C)RichardR.Eckert

16. Hello_in_windowExampleProgram •RespondstoPaintEventbydisplaying‘HelloWorld’inwindow’sclientareausingseveraldifferentBrushes •ManualProject -DefineHandlerandAttachittoPainteventmanually •DesignerProject -SelectthePainteventintheform’sPropertieswindow •Clickonlightningbolt •Doubleclickon"Paint"event -Attachmentofhandlerusingitsdelegateisdoneautomatically -Skeletonhandlercodegeneratedautomatically (C)RichardR.Eckert AnAlternativetoInstallingEventHandlers: OverridinginsteadofAttaching •Inanyclassderivedfrom‘Control’(e.g.‘Form’), itsprotectedOnPaint()andothereventhandlerscanbeoverridden: protectedoverridevoidOnPaint(PaintEventArgspea) { //Paintingcodegoeshere }; -Avoidshavingtoattachthehandlertotheeventusingthedelegate •SeeHelloWorld_overrideexampleprogram (C)RichardR.Eckert

17. ASeparateClassforMain() •Analternativewayoforganizinga WindowsFormapplication: -DefinetheForminoneclass -PlacetheMain()functioninanotherclass -VisualStudio2008designerdoesthis automatically -Coulddoitmanually •SeeSeparateMainexampleprogram (C)RichardR.Eckert InheritingFormClasses •JustasyourForminheritsfrom ‘System.Windows.Forms.Form’,youcansetupanewFormthatinheritsfromapreviouslydefinedForm •BesureitsMain()includeskeyword‘new’ •AndthatVisualStudioknowswhichclass’Main() istheentrypoint: -Inproject’sPropertiesboxselect‘PropertyPages’icon •‘CommonProperties’|‘General’|Application’|‘Startup Object’ •Select‘InheritHelloWorld’ •SeeHelloWorld_inheritexample (C)RichardR.Eckert

18. MultipleHandlers •Anadvantageofthedelegatemechanismisthatmultiplehandlersofthesameeventcanbeused •Justattacheachhandlertotheevent -Forexample: Form.Paint+=newPaintEventHandler(PaintHandler1); Form.Paint+=newPaintEventHandler(PaintHandler2); •Andthenwritethehandlers •Eachtimetheeventoccurs,allhandlerswillbecalledinsequence •SeeTwoPaintHandlersexample (C)RichardR.Eckert SomeotherGDI+DrawingMethods –DrawArc(); –DrawEllipse(); –DrawLine(); –DrawPolygon(); –DrawRectangle(); –FillEllipse(); –FillPolygon(); –FillRectangle(); –Lotsofothersin‘Graphics’class •Seeonlinehelponvariousoverloadedformsofcallingthese functions (C)RichardR.Eckert

19. RandomRectanglesExampleProgram –MakesuseofFillRectangle()GDI+method –‘Random’classcontainsmanymethodstogeneraterandomnumbers Randomr=newRandom(); –InstantiatesanewRandomobjectandseedsthepseudo-randomnumbergenerator •The‘Next()’methodactuallygeneratesthenumber –ManyoverloadedformsofNext() •Gettingarandomcolor: Colorc=Color.fromArgb(r.Next(256),r.Next(256),r.Next(256)); –UseForm’sClientSizePropertytogetwidthandheightofwindow –Drawfilledrectanglewithrandomsizeandcolor: •UseFillRectangle()andMath.Min(),Math.Abs() (C)RichardR.Eckert