advanced.c#.topzhujia

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1、AdvancedC#H.MössenböckUniversityofLinz,Austriamoessenboeck@ssw.uni-linz.ac.atContents•Inheritance•Interfaces•Delegates•Exceptions•NamespacesandAssemblies•Attributes•Threads•XMLComments1Inheritance2SyntaxclassA{//baseclassinta;publicA(){...}publicvoidF()

2、{...}}classB:A{//subclass(inheritsfromA,extendsA)intb;publicB(){...}publicvoidG(){...}}•BinheritsaandF(),itaddsbandG()-constructorsarenotinherited-inheritedmethodscanbeoverridden(seelater)•Singleinheritance:aclasscanonlyinheritfromonebaseclass,butitcani

3、mplementmultipleinterfaces.•Aclasscanonlyinheritfromaclass,notfromastruct.•Structscannotinheritfromanothertype,buttheycanimplementmultipleinterfaces.•Aclasswithoutexplicitbaseclassinheritsfromobject.3AsignmentsandTypeChecksclassA{...}classB:A{...}classC

4、:B{...}AssignmentsAa=newA();//statictypeofa:thetypespecifiedinthedeclaration(hereA)//dynamictypeofa:thetypeoftheobjectina(herealsoA)a=newB();//dynamictypeofaisBa=newC();//dynamictypeofaisCBb=a;//forbidden;compilationerrorRuntimetypechecksa=newC();if(ais

5、C)...//true,ifdynamictypeofaisCorasubclass;otherwisefalseif(aisB)...//trueif(aisA)...//true,butwarningbecauseitmakesnosensea=null;if(aisC)...//false:ifa==null,aisTalwaysreturnsfalse4CheckedTypeCastsCastAa=newC();Bb=(B)a;//if(aisB)stat.type(a)isBinthisex

6、pression;elseexceptionCc=(C)a;a=null;c=(C)a;//okÎnullcanbecastedtoanyreferencetypeasAa=newC();Bb=aasB;//if(aisB)b=(B)a;elseb=null;Cc=aasC;a=null;c=aasC;//c==null5OverridingofMethodsOnlymethodsthataredeclaredasvirtualcanbeoverriddeninsubclassesclassA{pub

7、licvoidF(){...}//cannotbeoverriddenpublicvirtualvoidG(){...}//canbeoverriddeninasubclass}OverridingmethodsmustbedeclaredasoverrideclassB:A{publicvoidF(){...}//warning:hidesinheritedF()ÎusenewpublicvoidG(){...}//warning:hidesinheritedG()Îusenewpublicover

8、ridevoidG(){//ok:overridesinheritedG...base.G();//callsinheritedG()}}•Methodsignaturesmustbeidentical-samenumberandtypesofparameters(includingfunctiontype)-samevisibility(public,protected,...).•Propertiesandindexerscanalsobeoverr