外文翻译--准备将 Visual Basic 6.0 应用程序升级到 Visual Basic.NET.doc -- 5 元

英文资料1PreparingYourVisualBasic6.0ApplicationsfortheUpgradetoVisualBasic.NETOverviewThisdocumentprovidesrecommendationsfordevelopersusingMicrosoft®VisualBasic®whoareplanningtoupgradetheirapplicationstoMicrosoftVisualBasic.NET.VisualBasic.NETwillopenandupgradeVisualBasic6.0projectstoVisualBasic.NETtechnologies,butinmostcasesyouwillneedtomakesomemodificationstoyourprojectsafterbringingthemintoVisualBasic.NET.ThepurposeofthisdocumentistorecommendhowtodesignandimplementyourcurrentVisualBasicprojectstominimizethenumberofchangesyouwillneedtomakewhentheyareupgradedtoVisualBasic.NET.Whereappropriate,weusenewlanguageconstructshowever,thisdocumentisnotintendedtobeaVisualBasic.NETlanguagereference.WhatIsVisualBasic.NETVisualBasic.NETisthenextversionofVisualBasic.RatherthansimplyaddingsomenewfeaturestoVisualBasic6.0,MicrosofthasreengineeredtheproducttomakeiteasierthaneverbeforetowritedistributedapplicationssuchasWebandenterprisentiersystems.VisualBasic.NEThastwonewformspackagesWindowsFormsandWebFormsanewversionofADOforaccessingdisconnecteddatasourcesandstreamlinedlanguage,removinglegacykeywords,improvingtypesafety,andexposinglowlevelconstructsthatadvanceddevelopersrequire.ThesenewfeaturesopennewdoorsfortheVisualBasicdeveloperWithWebFormsandADO.NET,youcannowrapidlydevelopscalableWebsiteswithinheritance,thelanguagenowtrulysupportsobjectorientedprogrammingWindowsFormsnativelysupportsaccessibilityandvisualinheritanceanddeployingyourapplicationsisnowassimpleascopyingyourexecutablesandcomponentsfromdirectorytodirectory.VisualBasic.NETisnowfullyintegratedwiththeotherMicrosoftVisualStudio.NETlanguages.Notonlycanyoudevelopapplicationcomponentsin英文资料2differentprogramminglanguages,yourclassescannowinheritfromclasseswritteninotherlanguagesusingcrosslanguageinheritance.Withtheunifieddebugger,youcannowdebugmultiplelanguageapplications,irrespectiveofwhethertheyarerunninglocallyoronremotecomputers.Finally,whateverlanguageyouuse,theMicrosoft.NETFrameworkprovidesarichsetofAPIsforMicrosoftWindows®andtheInternet.WhyIsVisualBasic.NETNot100CompatibleThereweretwooptionstoconsiderwhendesigningVisualBasic.NETretrofittheexistingcodebasetorunontopofthe.NETFramework,orbuildfromthegroundup,takingfulladvantageoftheplatform.Todeliverthefeaturesmostrequestedbycustomersforexample,inheritance,threading,toprovidefullanduninhibitedaccesstotheplatform,andtoensurethatVisualBasicmovesforwardintothenextgenerationofWebapplications,therightdecisionwastobuildfromthegrounduponthenewplatform.Forexample,manyofthenewfeaturesfoundinWindowsFormscouldhavebeenaddedtotheexistingcodebaseasnewcontrolsormoreproperties.However,thiswouldhavebeenatthecostofalltheothergreatfeaturesinherenttoWindowsForms,suchassecurityandvisualinheritance.OneofourmajorgoalswastoensureVisualBasiccodecouldfullyinteroperatewithcodewritteninotherlanguages,suchasMicrosoftVisualC™orMicrosoftVisualC®,andenabletheVisualBasicdevelopertoharnessthepowerofthe.NETFrameworksimply,withoutresortingtotheprogrammingworkaroundstraditionallyrequiredtomakeWindowsAPIswork.VisualBasicnowhasthesamevariabletypes,arrays,userdefinedtypes,classes,andinterfacesasVisualCandanyotherlanguagethattargetstheCommonLanguageRuntimehowever,wehadtoremovesomefeatures,suchasfixedlengthstringsandnonzerobasedarraysfromthelanguage.VisualBasicisnowatrueobjectorientedlanguagesomeunintuitiveandinconsistentfeatureslikeGoSub/ReturnandDefInthavebeenremovedfromthelanguage.英文资料3TheresultisareenergizedVisualBasic,whichwillcontinuetobethemostproductivetoolforcreatingWindowsbasedapplications,andisnowpositionedtobethebesttoolforcreatingthenextgenerationWebsites.UpgradingtoVisualBasic.NETVisualBasic.NETenablesafundamentalshiftfromtraditionalWindowsdevelopmenttobuildingnextgenerationWebandntierapplications.Forthisreason,yourcodewillneedtobeupgradedtotakeadvantageofVisualBasic.NET.ThishappensautomaticallywhenyouopenaVisualBasic6.0projectinVisualBasic.NETtheUpgradeWizardstepsyouthroughtheupgradeprocessandcreatesanewVisualBasic.NETprojectyourexistingprojectisleftunchanged.ThisisaonewayprocessthenewVisualBasic.NETprojectcannotbeopenedinVisualBasic6.0.Whenyourprojectisupgraded,thelanguageismodifiedforanysyntaxchangesandyourVisualBasic6.0FormsareconvertedtoWindowsForms.Inmostcases,youwillhavetomakesomechangestoyourcodeafteritisupgraded.ThisisrequiredbecausecertainobjectsandlanguagefeatureseitherhavenoequivalentinVisualBasic.NET,orhaveanequivalenttoodissimilarforanautomaticupgrade.Aftertheupgrade,youmayalsowanttochangeyourapplicationtotakeadvantageofsomeofthenewfeaturesinVisualBasic.NET.WorkingwithBothVisualBasic6.0andVisualBasic.NETVisualBasic.NETsupportsupgradingVisualBasic6.0projectsifyouhaveaprojectwritteninVisualBasicversions1to5,werecommendyouloaditintoVB6choosingtoupgradeMicrosoftActiveX®controls,compile,andsavetheprojectbeforeupgradingittoVisualBasic.NET.BothVisualBasic.NETandVisualBasic6.0canbeinstalledonthesamecomputerandrunatthesametime.Likewise,applicationswritteninVisualBasic.NETandVisualBasic6.0canbeinstalledandexecutedonthesamecomputer.ComponentswritteninVisualBasic.NETcaninteroperatewithCOMcomponentswritteninearlierversionsofVisualBasicandotherlanguages.Forexample,youcandropanActiveXcontrolwritteninVisualBasic6.0ontoaVisualBasic.NET英文资料4WindowsForm,useaVisualBasic6.0COMobjectfromaVisualBasic.NETclasslibrary,oraddareferencetoaVisualBasic.NETlibrarytoaVisualBasic6.0executable.ComponentscompiledwithVisualBasic.NEThavesubtleruntimedifferencesfromcomponentscompiledwithVisualBasic6.0.Forstarters,becauseVisualBasic.NETobjectsarereleasedthroughgarbagecollection,whenobjectsareexplicitlydestroyed,theremaybealagbeforetheyareactuallyremovedfrommemory.Thereareadditionaldifferencessuchasthevariant/objectchangesdescribedlaterinthisdocument.ThecombinedresultofthesedifferencesisthatVisualBasic.NETapplicationswillhavesimilarbutnotidenticalruntimebehaviortoVisualBasic6.0applications.Inaddition,VisualBasic.NETmakesbinarycompatibilitybetweenVisualBasic.NETcomponentsandthoseinVisualBasic6.0unnecessary.Componentsnowhaveamorerobustversioninganddeploymentsystemthaneverbefore,filescanbedeployedbysimplycopyingtoadirectorynomoreRegSvr32,andupgradingtoanewversionofacomponentisassimpleasreplacingtheoldfilewithanewfile.Allyouhavetodoisensureclassesandmethodsarecompatiblewiththepreviousversion.ArchitectureRecommendationsThe.NETplatformimprovesuponpreviousarchitectures,andaddsgreatersupportforscalabilityanddistributedapplicationsthoughdisconnecteddataaccess,HTTPbasedmessagetransport,andfilecopybaseddeploymentnomoreregisteringofcomponents.Tobesttakeadvantageofthesefeatures,youshoulddesignyourapplicationswithanarchitecturesimilartothatyouwoulduseinVisualBasic.NET.BrowserbasedApplicationsVisualBasic6.0andMicrosoftVisualStudio®6.0offeredseveraltechnologiesforcreatingbrowserbasedInternetandintranetapplicationsWebclassesDHTMLprojects