ASP NET入门C#版毕业论文外文文献翻译.docx

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… BeginningASP.NET2.0inC#

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… ASP（ActiveServerPages）isarelativelynewtechnologythat’salready

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… leaptthroughseveralstagesofevolution.Itwasintroducedaboutsevenyears

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… agoasaneasywaytoadddynamiccontenttoordinarywebpages.Sincethen,

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… it’sgrownintosomethingmuchmoreambitious:

aplatformforcreating

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… advancedwebapplications,includingmerceshops,data.drivenportalsites,

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… andjustaboutanythingelseyoucanfindontheInternet.ASP.NET2.0isthe

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… latestversionofASP,anditrepresentsthemostdramaticchangeyet.With

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… ASP.NET,developersnolongerneedtopastetogetherajumbleofHTMLand

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… scriptcodeinordertoprogramtheWeb.Instead,youcancreatefull.scaleweb

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订 applicationsusingnothingbutcodeandadesigntoolsuchasVisualStudio2008

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… Thecostofallthisinnovationisthelearningcurve.Notonlydo youneedto

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… learnhowtouseanadvanceddesigntool（VisualStudio）andatoolkitofobjects

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… （the.NETFramework）,youalsoneedtomasteraprogramminglanguagesuch

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… asC#.TheInternetbeganinthelate1960sasanexperiment.Itsgoalwasto

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… createatrulyresilientinformationnetwork—onethatcouldwithstandthelossof

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… severalcomputerswithoutpreventingtheothersfromcommunicating.Driven

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… bypotentialdisasterscenarios（suchasnuclearattack）,theU.S.Departmentof

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… Defenseprovidedtheinitialfunding.TheearlyInternetwasmostlylimitedto

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… educationalinstitutionsanddefensecontractors.Itflourishedasatoolfor

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… academic collaboration, allowing researchers across the globe to share

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… information.Intheearly1990s,modemswerecreatedthatcouldworkoverexistingphonelines,andtheInternetbegantoopenuptocommercialusers.In

1993,thefirstHTMLbrowserwascreated,andtheInternetrevolutionbegan.It

… wouldbedifficulttodescribeearlywebsitesaswebapplications.Instead,the

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… firstgenerationofwebsitesoftenlookedmorelikebrochures,consistingmostly

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… offixedHTMLpagesthatneededtobeupdatedbyhand.BasicHTMLpageisa

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… littlelikeaword.processingdocument—itcontainsformattedcontentthatcanbe

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… displayedonyourcomputer,butitdoesn’tactuallydoanything.Thefollowing

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装 exampleshowsHTMLatitssimplest,withadocumentthatcontainsaheading

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… andsinglelineoftext:

AnHTMLdocumenthastwotypesofcontent:

thetext

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… andthetagsthattellthebrowserhowtoformatit.Thetagsareeasily

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… recognizable,becausetheyoccurinsideangledbrackets（<>）.HTMLdefines

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… tagsfordifferentlevelsofheadings,paragraphs,hyperlinks,italicandbold

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… formatting,horizontallines,andsoon.Forexample,

SomeText

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… thebrowsertodisplaySomeTextintheHeading1style,whichusesalarge,

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… boldfont.Figure1.1showsthesimpleHTMLpageinabrowser.HTML2.0

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… introducedthefirstseedofwebprogrammingwithatechnologycalledHTML

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… forms.HTMLformsexpandHTMLsothatitincludesnotonlyformattingtags

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… butalsotagsforgraphicalwidgets,orcontrols.Thesecontrolsincludecommon

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… ingredientssuchasdrop.downlists,textboxes,andbuttons.Here’sasample

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… web pagecreated with HTMLformcontrols:

HTMLforms allow web

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线 applicationdeveloperstodesignstandardinputpages.Whentheuserclicksthe

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… SubmitbuttononthepageshowninFigure1.2,allthedataintheinputcontrols

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… （inthiscase,thetwocheckboxes）ispatchedtogetherintoonelongstringand

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… senttothewebserver.Ontheserverside,acustomapplicationreceivesand

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… processesthedata.Amazinglyenough,thecontrolsthatwerecreatedforHTML

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… formsmorethantenyearsagoarestillthebasicfoundationthat you’lluseto

builddynamicASP.NETpages!

Thedifferenceisthetypeofapplicationthat

… runsontheserverside.Inthepast, whentheuserclickedabuttononaform

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… page,theinformationmighthavebeene.mailedtoasetaccountorsenttoan

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… applicationontheserverthatusedthechallengingCGI（CommonGateway

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… Interface）standard.Today,you’llworkwiththemuchmorecapableandelegant

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… ASP.NETplatform.TounderstandwhyASP.NETwascreated,ithelpsto

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装 understandtheproblemsofotherwebdevelopmenttechnologies.Withthe

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… originalCGIstandard,forexample,thewebservermustlaunchacompletely

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… separateinstanceoftheapplicationforeachwebrequest.Ifthewebsiteis

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… popular,thewebservermuststruggleundertheweightofhundredsofseparate

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… copiesoftheapplication,eventuallybecomingavictimofitsownsuccessor

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… counterthisproblem,MicrosoftdevelopedISAPI（InternetServerApplication

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… ProgrammingInterface）,ahigher.levelprogrammingmodel.ISAPIsolvedthe

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… performanceproblembutatthecostofsignificantcomplexity.EvenafterISAPI

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… developersmasterthetrickyC++programminglanguage,theystilllieawakeat

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… nightworryingaboutconfoundingissuessuchasmultithreading. ISAPI

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… programmingisdefinitelynotforthefainthearted.SAPIneverreallywentaway.

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… Instead,Microsoftusedittobuildhigher.leveldevelop.mintplatforms,suchas

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… ASPandASP.NET.Bothofthesetechnologiesallowdeveloperstoprogram

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线 dynamicwebpageswithoutworryingaboutthelow.levelimplementationdetails.

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… Forthatreason,bothplatformshavebecomeincrediblysuccessful.Theoriginal

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… ASPplatformgarneredahugeaudienceofnearlyonemilliondevelopers.When

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… ASP.NETwasfirstreleased,itgeneratedevenmoreinterestasthecenterpieceof

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… the.NETFrame.work.Infact,ASP.NET1.0wasenthusiasticallyputtoworkin

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… dozensoflarge.scalecommercialwebsitesevenwhenitwasonlyinlatebeta.

Despitehavingsimilarunderpinnings,ASPandASP.NETareradicallydifferent.

… ASPis ascript.based programminglanguage that requiresa thorough

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… understandingofHTMLandagooddealofpainfulcoding.ASP.NET,onthe

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… otherhand,isanobject.orientedpro.gammingmodelthatletsyouputtogethera

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… webpageaseasilyasyouwouldbuildaWindowsapplication.Inmanyrespects,

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… it’seasiertolearnASP.NETthantomasterASP,eventhoughASP.NETisfar

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装 morepowerful.Atthesametimethatserver.sidewebdevelopmentwasmoving

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… throughanalphabetsoupoftechnologies,anewtypeofprogrammingwas

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… gainingpopularity.Developersbegantoexperimentwiththedifferentwaysthey

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… couldenhancewebpagesbyembed.dingmultimediaandminiatureappletsbuilt

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… withJavaScript,DHTML（DynamicHTML）,andJavacode.Theseclient.side

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… technologiesdon’tinvolveanyserverprocessing. Instead,thecomplete

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… applicationisdownloadedtotheclientbrowser,whichexecutesitlocally.The

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… greatestproblemwithclient.sidetechnologiesisthattheyaren’tsupported

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… equallybyallbrowsersandoperatingsystems.Oneofthereasonsthatweb

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… developmentissopopularinthefirstplaceisbecausewebapplicationsdon’t

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… requiresetupCDs,down.loads,andothertedious（anderror.prone）deployment

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… steps.Instead,awebapplicationcanbeusedonanycomputerthathasInternet

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… access.Butwhendevelopersuseclient.sidetechnologies,theyencounterafew

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线 familiarheadaches.Suddenly,cross.browsercompatibilitybecomesaproblem.

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… Developersareforcedtotesttheirwebsiteswithoperatingsystemsand

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… browsers,andtheymightevenneedtodistributebrowserupdatestotheirclients.

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… Inotherwords,theclient.sidemodelsacrificessomeofthemostimportant

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… benefitsofwebdevelopment.orthatreason,ASP.NETisdesignedasa

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… server.sidetechnology.AllASP.NETcodeexecutesontheserver.Whenthecode

isfinishedexecuting,theuserreceivesanordinaryHTMLpage,whichcanbe

… viewedinanybrowser.Figure1.3showsthedifferencebetweentheserver.side

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… andclient.sidemodel.Thesearesomeotherreasonsforavoidingclient.side

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… programming:

Isolation:

Client.sidecodecan’taccessserver.sideresources.For

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… example,aclient.sideapplicationhasnoeasywaytoreadafileorinteractwith

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… adatabaseontheserver（atleastnotwithoutrunningintoproblemswithsecurity

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装 andbrowsercompatibility）.Security:

Enduserscanviewclient.sidecode.And

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… oncemalicioususersunderstandhowanapplicationworks,theycanoften

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… tamperwithit.mecases,ASP.NETallowsyoutocombinethebestofclient.side

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… programmingwithserver.sideprogramming.Forexample,thebestASP.NET

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… controlscanintelligentlydetectthefeaturesoftheclientbrowser.Ifthebrowser

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… supportsJavaScript,thesecontrolswillreturnawebpagethatincorporates

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… JavaScriptforaricher,moreresponsiveuserinterface.However,nomatterwhat

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… thecapabilitiesofthebrowser,yourcodeisalwaysexecutedontheserver.State

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… limitations:

Toensureoptimumperformance,theWebisbuiltonstateless

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… protocols,whichmeansassoonasapageissenttoauser,theconnectionis

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… closedandanyuser.specificinformationisdiscarded.ASPincludesasession

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… statefeaturethatallowsprogrammerstoworkaroundthisproblem.Using

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… sessionstate,awebapplicationcanretaintemporary