C#+Interview+Questions++Answers+2Word文件下载.docx
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C#+Interview+Questions++Answers+2Word文件下载.docx
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6.Describetheaccessibilitymodifier‘protectedinternal’.
It’savailabletoderivedclassesandclasseswithinthesameAssembly(andnaturallyfromthebaseclassit’sdeclaredin).
7.C#providesadefaultconstructorforme.Iwriteaconstructorthattakesastringasaparameter,butwanttokeepthenoparameterone.HowmanyconstructorsshouldIwrite?
Two.Onceyouwriteatleastoneconstructor,C#cancelsthefreebieconstructor,andnowyouhavetowriteoneyourself,evenifthere’snoimplementationinit.
8.What’sthetop.NETclassthateverythingisderivedfrom?
System.Object.
9.How’smethodoverridingdifferentfromoverloading?
Whenoverriding,youchangethemethodbehaviorforaderivedclass.Overloadingsimplyinvolveshavingamethodwiththesamenamewithintheclass.
10.Whatdoesthekeywordvirtualmeaninthemethoddefinition?
Themethodcanbeover-ridden.
11.Canyoudeclaretheoverridemethodstaticwhiletheoriginalmethodisnon-static?
No,youcan’t,thesignatureofthevirtualmethodmustremainthesame,onlythekeywordvirtualischangedtokeywordoverride.
12.Canyouoverrideprivatevirtualmethods?
No,moreover,youcannotaccessprivatemethodsininheritedclasses,havetobeprotectedinthebaseclasstoallowanysortofaccess.
13.Canyoupreventyourclassfrombeinginheritedandbecomingabaseclassforsomeotherclasses?
Yes,that’swhatkeywordsealedintheclassdefinitionisfor.Thedevelopertryingtoderivefromyourclasswillgetamessage:
cannotinheritfromSealedclassWhateverBaseClassName.It’sthesameconceptasfinalclassinJava.
14.Canyouallowclasstobeinherited,butpreventthemethodfrombeingover-ridden?
Yes,justleavetheclasspublicandmakethemethodsealed.
15.What’sanabstractclass?
Aclassthatcannotbeinstantiated.AconceptinC++knownaspurevirtualmethod.Aclassthatmustbeinheritedandhavethemethodsover-ridden.Essentially,it’sablueprintforaclasswithoutanyimplementation.
16.Whendoyouabsolutelyhavetodeclareaclassasabstract(asopposedtofree-willededucatedchoiceordecisionbasedonUMLdiagram)?
Whenatleastoneofthemethodsintheclassisabstract.Whentheclassitselfisinheritedfromanabstractclass,butnotallbaseabstractmethodshavebeenover-ridden.
17.What’saninterfaceclass?
It’sanabstractclasswithpublicabstractmethodsallofwhichmustbeimplementedintheinheritedclasses.
18.Whycan’tyouspecifytheaccessibilitymodifierformethodsinsidetheinterface?
Theyallmustbepublic.Therefore,topreventyoufromgettingthefalseimpressionthatyouhaveanyfreedomofchoice,youarenotallowedtospecifyanyaccessibility,it’spublicbydefault.
19.Canyouinheritmultipleinterfaces?
Yes,whynot.
Andiftheyhaveconflictingmethodnames?
It’suptoyoutoimplementthemethodinsideyourownclass,soimplementationisleftentirelyuptoyou.Thismightcauseaproblemonahigher-levelscaleifsimilarlynamedmethodsfromdifferentinterfacesexpectdifferentdata,butasfarascompilercaresyou’reokay.
20.What’sthedifferencebetweenaninterfaceandabstractclass?
Intheinterfaceallmethodsmustbeabstract;
intheabstractclasssomemethodscanbeconcrete.Intheinterfacenoaccessibilitymodifiersareallowed,whichisokinabstractclasses.
21.Howcanyouoverloadamethod?
Differentparameterdatatypes,differentnumberofparameters,differentorderofparameters.
22.Ifabaseclasshasabunchofoverloadedconstructors,andaninheritedclasshasanotherbunchofoverloadedconstructors,canyouenforceacallfromaninheritedconstructortoanarbitrarybaseconstructor?
Yes,justplaceacolon,andthenkeywordbase(parameterlisttoinvoketheappropriateconstructor)intheoverloadedconstructordefinitioninsidetheinheritedclass.
23.What’sthedifferencebetweenSystem.StringandSystem.StringBuilderclasses?
System.Stringisimmutable;
System.StringBuilderwasdesignedwiththepurposeofhavingamutablestringwhereavarietyofoperationscanbeperformed.
24.What’stheadvantageofusingSystem.Text.StringBuilderoverSystem.String?
StringBuilderismoreefficientinthecases,wherealotofmanipulationisdonetothetext.Stringsareimmutable,soeachtimeit’sbeingoperatedon,anewinstanceiscreated.
25.CanyoustoremultipledatatypesinSystem.Array?
No.
26.What’sthedifferencebetweentheSystem.Array.CopyTo()andSystem.Array.Clone()?
Thefirstoneperformsadeepcopyofthearray,thesecondoneisshallow.
Howcanyousorttheelementsofthearrayindescendingorder?
BycallingSort()andthenReverse()methods.
What’sthe.NETdatatypethatallowstheretrievalofdatabyauniquekey?
HashTable.
27.What’sclassSortedListunderneath?
AsortedHashTable.
28.Willfinallyblockgetexecutediftheexceptionhadnotoccurred?
Yes.
29.What’stheC#equivalentofC++catch(…),whichwasacatch-allstatementforanypossibleexception?
AcatchblockthatcatchestheexceptionoftypeSystem.Exception.Youcanalsoomittheparameterdatatypeinthiscaseandjustwritecatch{}.
30.Canmultiplecatchblocksbeexecuted?
No,oncethepropercatchcodefiresoff,thecontrolistransferredtothefinallyblock(ifthereareany),andthenwhateverfollowsthefinallyblock.
31.Whyisitabadideatothrowyourownexceptions?
Well,ifatthatpointyouknowthatanerrorhasoccurred,thenwhynotwritethepropercodetohandlethaterrorinsteadofpassinganewExceptionobjecttothecatchblock?
Throwingyourownexceptionssignifiessomedesignflawsintheproject.
32.What’sadelegate?
Adelegateobjectencapsulatesareferencetoamethod.InC++theywerereferredtoasfunctionpointers.
33.What’samulticastdelegate?
It’sadelegatethatpointstoandeventuallyfiresoffseveralmethods.
34.How’stheDLLHellproblemsolvedin.NET?
Assemblyversioningallowstheapplicationtospecifynotonlythelibraryitneedstorun(whichwasavailableunderWin32),butalsotheversionoftheassembly.
35.Whatarethewaystodeployanassembly?
AnMSIinstaller,aCABarchive,andXCOPYcommand.
36.What’sasatelliteassembly?
Whenyouwriteamultilingualormulti-culturalapplicationin.NET,andwanttodistributethecoreapplicationseparatelyfromthelocalizedmodules,thelocalizedassembliesthatmodifythecoreapplicationarecalledsatelliteassemblies.
37.Whatnamespacesarenecessarytocreatealocalizedapplication?
System.Globalization,System.Resources.
38.What’sthedifferencebetween//comments,/**/commentsand///comments?
Single-line,multi-lineandXMLdocumentationcomments.
39.HowdoyougeneratedocumentationfromtheC#filecommentedproperlywithacommand-linecompiler?
Compileitwitha/docswitch.
40.What’sthedifferencebetween<
c>
and<
code>
XMLdocumentationtag?
Singlelinecodeexampleandmultiple-linecodeexample.
41.IsXMLcase-sensitive?
Yes,so<
Student>
student>
aredifferentelements.
42.Whatdebuggingtoolscomewiththe.NETSDK?
CorDBG–command-linedebugger,andDbgCLR–graphicdebugger.VisualStudio.NETusestheDbgCLR.TouseCorDbg,youmustcompiletheoriginalC#fileusingthe/debugswitch.
43.WhatdoestheThiswindowshowinthedebugger?
Itpointstotheobjectthat’spointedtobythisreference.Object’sinstancedataisshown.
44.Whatdoesassert()do?
Indebugcompilation,asserttakesinaBooleanconditionasaparameter,andshowstheerrordialogiftheconditionisfalse.Theprogramproceedswithoutanyinterruptioniftheconditionistrue.
45.What’sthedifferencebetweentheDebugclassandTraceclass?
Documentationlooksthesame.
UseDebugclassfordebugbuilds,useTraceclassforbothdebugandreleasebuilds.
46.WhyaretherefivetracinglevelsinSystem.Diagnostics.TraceSwitcher?
Thetracingdumpscanbequiteverboseandforsomeapplicationsthatareconstantlyrunningyouruntheriskofoverloadingthemachineandtheharddrivethere.FivelevelsrangefromNonetoVerbose,allowingtofine-tunethetracingactivities.
47.WhereistheoutputofTextWriterTraceListenerredirected?
TotheConsoleoratextfiledependingontheparameterpassedtotheconstructor.
48.HowdoyoudebuganASP.NETWebapplication?
Attachtheaspnet_wp.exeprocesstotheDbgClrdebugger.
49.Whatarethreetestcasesyoushouldgothroughinunittesting?
Positivetestcases(correctdata,correctoutput),negativetestcases(brokenormissingdata,properhandling),exceptiontestcases(exceptionsarethrownandcaughtproperly).
50.CanyouchangethevalueofavariablewhiledebuggingaC#application?
Yes,ifyouaredebuggingviaVisualStudio.NET,justgotoImmediatewindow.
Explainthethreeservicesmodel(three-tierapplication).
Presentation(UI),business(logicandunderlyingcode)anddata(fromstorageorothersources).
51.WhatareadvantagesanddisadvantagesofMicrosoft-provideddataproviderclasses
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