英文文献与翻译Word格式.docx

英文文献与翻译Word格式.docx

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The.NETFrameworkClassLibrary

ImaginethatyouareMicrosoft.Imaginethatyouhavetosupportmultipleprogramminglanguages—suchasVisualBasic,JScript,andC++.Agreatdealofthefunctionalityoftheseprogramminglanguagesoverlaps.Forexample,foreachlanguage,youwouldhavetoincludemethodsforaccessingthefilesystem,workingwithdatabases,andmanipulatingstrings.

Furthermore,theselanguagescontainsimilarprogrammingconstructs.Everylanguage,forexample,canrepresentloopsandconditionals.EventhoughthesyntaxofaconditionalwritteninVisualBasicdiffersfromthesyntaxofaconditionalwritteninC++,theprogrammingfunctionisthesame.

Finally,mostprogramminglanguageshavesimilarvariabledatatypes.Inmostlanguages,youhavesomemeansofrepresentingstringsandintegers,forexample.Themaximumandminimumsizeofanintegermightdependonthelanguage,butthebasicdatatypeisthesame.

Maintainingallthisfunctionalityformultiplelanguagesrequiresalotofwork.Whykeepreinventingthewheel?

Wouldn'

titbeeasiertocreateallthisfunctionalityonceanduseitforeverylanguage?

The.NETFrameworkClassLibrarydoesexactlythat.Itconsistsofavastsetofclassesdesignedtosatisfyanyconceivableprogrammingneed.Forexample,the.NETframeworkcontainsclassesforhandlingdatabaseaccess,workingwiththefilesystem,manipulatingtext,andgeneratinggraphics.Inaddition,itcontainsmorespecializedclassesforperformingtaskssuchasworkingwithregularexpressionsandhandlingnetworkprotocols.

The.NETframework,furthermore,containsclassesthatrepresentallthebasicvariabledatatypessuchasstrings,integers,bytes,characters,andarrays.

Mostimportantly,forpurposesofthisbook,the.NETFrameworkClassLibrarycontainsclassesforbuildingASP.NETpages.Youneedtounderstand,however,thatyoucanaccessanyofthe.NETframeworkclasseswhenyouarebuildingyourASP.NETpages.

UnderstandingNamespaces

Asyoumightguess,the.NETframeworkishuge.Itcontainsthousandsofclasses（over3,400）.Fortunately,theclassesarenotsimplyjumbledtogether.Theclassesofthe.NETframeworkareorganizedintoahierarchyofnamespaces.

ASPClassicNote

InpreviousversionsofActiveServerPages,youhadaccesstoonlyfivestandardclasses（theResponse,Request,Session,Application,andServerobjects）.ASP.NET,incontrast,providesyouwithaccesstoover3,400classes!

Anamespaceisalogicalgroupingofclasses.Forexample,alltheclassesthatrelatetoworkingwiththefilesystemaregatheredtogetherintotheSystem.IOnamespace.

Thenamespacesareorganizedintoahierarchy（alogicaltree）.AttherootofthetreeistheSystemnamespace.Thisnamespacecontainsalltheclassesforthebasedatatypes,suchasstringsandarrays.Italsocontainsclassesforworkingwithrandomnumbersanddatesandtimes.

Youcanuniquelyidentifyanyclassinthe.NETframeworkbyusingthefullnamespaceoftheclass.Forexample,touniquelyrefertotheclassthatrepresentsafilesystemfile（theFileclass）,youwouldusethefollowing:

System.IO.File

System.IOreferstothenamespace,andFilereferstotheparticularclass.

NOTE

Youcanviewallthenamespacesofthestandardclassesinthe.NETFrameworkClassLibrarybyviewingtheReferenceDocumentationforthe.NETFramework.

StandardASP.NETNamespaces

TheclassescontainedinaselectnumberofnamespacesareavailableinyourASP.NETpagesbydefault.（Youmustexplicitlyimportothernamespaces.）ThesedefaultnamespacescontainclassesthatyouusemostofteninyourASP.NETapplications:

System—Containsallthebasedatatypesandotherusefulclassessuchasthoserelatedtogeneratingrandomnumbersandworkingwithdatesandtimes.

System.Collections—Containsclassesforworkingwithstandardcollectiontypessuchashashtables,andarraylists.

System.Collections.Specialized—Containsclassesthatrepresentspecializedcollectionssuchaslinkedlistsandstringcollections.

System.Configuration—Containsclassesforworkingwithconfigurationfiles（Web.configfiles）.

System.Text—Containsclassesforencoding,decoding,andmanipulatingthecontentsofstrings.

System.Text.RegularExpressions—Containsclassesforperformingregularexpressionmatchandreplaceoperations.

System.Web—ContainsthebasicclassesforworkingwiththeWorldWideWeb,includingclassesforrepresentingbrowserrequestsandserverresponses.

System.Web.Caching—Containsclassesusedforcachingthecontentofpagesandclassesforperformingcustomcachingoperations.

System.Web.Security—ContainsclassesforimplementingauthenticationandauthorizationsuchasFormsandPassportauthentication.

System.Web.SessionState—Containsclassesforimplementingsessionstate.

System.Web.UI—ContainsthebasicclassesusedinbuildingtheuserinterfaceofASP.NETpages.

System.Web.UI.HTMLControls—ContainstheclassesfortheHTMLcontrols.

System.Web.UI.WebControls—ContainstheclassesfortheWebcontrols.

.NETFramework-CompatibleLanguages

Forpurposesofthisbook,youwillwritetheapplicationlogicforyourASP.NETpagesusingVisualBasicasyourprogramminglanguage.ItisthedefaultlanguageforASP.NETpages.AlthoughyousticktoVisualBasicinthisbook,youalsoneedtounderstandthatyoucancreateASP.NETpagesbyusinganylanguagethatsupportsthe.NETCommonLanguageRuntime.Outofthebox,thisincludesC#,JScript.NET,andtheManagedExtensionstoC++.

TheCDincludedwiththisbookcontainsC#versionsofallthecodesamples.

DozensofotherlanguagescreatedbycompaniesotherthanMicrosofthavebeendevelopedtoworkwiththe.NETframework.SomeexamplesoftheseotherlanguagesincludePython,SmallTalk,Eiffel,andCOBOL.Thismeansthatyoucould,ifyoureallywantedto,writeASP.NETpagesusingCOBOL.

RegardlessofthelanguagethatyouusetodevelopyourASP.NETpages,youneedtounderstandthatASP.NETpagesarecompiledbeforetheyareexecuted.ThismeansthatASP.NETpagescanexecuteveryquickly.

ThefirsttimeyourequestanASP.NETpage,thepageiscompiledintoa.NETclass,andtheresultingclassfileissavedbeneathaspecialdirectoryonyourservernamedTemporaryASP.NETFiles.ForeachandeveryASP.NETpage,acorrespondingclassfileappearsintheTemporaryASP.NETFilesdirectory.WheneveryourequestthesameASP.NETpageinthefuture,thecorrespondingclassfileisexecuted.

WhenanASP.NETpageiscompiled,itisnotcompileddirectlyintomachinecode.Instead,itiscompiledintoanintermediate-levellanguagecalledMicrosoftIntermediateLanguage（MSIL）.All.NET-compatiblelanguagesarecompiledintothisintermediatelanguage.

AnASP.NETpageisn'

tcompiledintonativemachinecodeuntilitisactuallyrequestedbyabrowser.Atthatpoint,theclassfilecontainedintheTemporaryASP.NETFilesdirectoryiscompiledwiththe.NETframeworkJustinTime（JIT）compilerandexecuted.

Themagicalaspectofthiswholeprocessisthatithappensautomaticallyinthebackground.AllyouhavetodoiscreateatextfilewiththesourcecodeforyourASP.NETpage,andthe.NETframeworkhandlesallthehardworkofconvertingitintocompiledcodeforyou.

ASPCLASSICNOTE

WhataboutVBScript?

BeforeASP.NET,VBScriptwasthemostpopularlanguagefordevelopingActiveServerPages.

ASP.NETdoesnotsupportVBScript,andthisisgoodnews.VisualBasicisasupersetofVBScript,whichmeansthatVisualBasichasallthefunctionalityofVBScriptandmore.So,youhavearichersetoffunctionsandstatementswithVisualBasic.

Furthermore,unlikeVBScript,VisualBasicisacompiledlanguage.ThismeansthatifyouuseVisualBasictorewritethesamecodethatyouwrotewithVBScript,youcangetbetterperformance.

IfyouhaveworkedonlywithVBScriptandnotVisualBasicinthepast,don'

tworry.SinceVBScriptissocloselyrelatedtoVisualBasic,you'

llfinditeasytomakethetransitionbetweenthetwolanguages.

MicrosoftincludesaninterestingtoolnamedtheILDisassembler（ILDASM）withthe.NETframework.YoucanusethistooltoviewthedisassembledcodeforanyoftheASP.NETclassesintheTemporaryASP.NETFilesdirectory.Itlistsallthemethodsandpropertiesoftheclassandenablesyoutoviewtheintermediate-levelcode.

ThistoolalsoworkswithalltheASP.NETcontrolsdiscussedinthischapter.Forexample,youcanusetheILDisassemblertoviewtheintermediate-levelcodefortheTextBoxcontrol（locatedinafilenamedSystem.Web.dll）.

IntroducingASP.NETControls

ASP.NETcontrolsprovidethedynamicandinteractiveportionsoftheuserinterfaceforyourWebapplication.ThecontrolsrenderthecontentthattheusersofyourWebsiteactuallyseeandinteractwith.Forexample,youcanusecontrolstocreateHTMLformelements,interactivecalendars,androtatingbanneradvertisements.

ASP.NETcontrolscoexistpeacefullywithHTMLcontent.Typically,youcreatethestaticareasofyourWebpageswithnormalHTMLcontentandcreatethedynamicorinteractiveportionswithASP.NETcontrols.

ThebestwaytounderstandhowASP.NETcontrolsworkinanHTMLpageistolookatasimpleWebFormsPage.

AddingApplicationLogictoanASP.NETPage

ThesecondbuildingblockofanASP.NETpageistheapplicationlogic,whic