外文翻译 - ASP.NET 技术

外文原文ASP.NETTechnique1.BuildingASP.NETPagesASP.NETandthe.NETFrameworkASP.NETispartofMicrosoftsoverall.NETframework,whichcontainsavastsetofprogrammingclassesdesignedtosatisfyanyconceivableprogrammingneed.Inthefollowingtwosections,youlearnhowASP.NETfitswithinthe.NETframework,andyoulearnaboutthelanguagesyoucanuseinyourASP.NETpages.The.NETFrameworkClassLibraryImaginethatyouareMicrosoft.ImaginethatyouhavetosupportmultipleprogramminglanguagessuchasVisualBasic,JScript,andC+.Agreatdealofthefunctionalityoftheseprogramminglanguagesoverlaps.Forexample,foreachlanguage,youwouldhavetoincludemethodsforaccessingthefilesystem,workingwithdatabases,andmanipulatingstrings.Furthermore,theselanguagescontainsimilarprogrammingconstructs.Everylanguage,forexample,canrepresentloopsandconditionals.EventhoughthesyntaxofaconditionalwritteninVisualBasicdiffersfromthesyntaxofaconditionalwritteninC+,theprogrammingfunctionisthesame.Finally,mostprogramminglanguageshavesimilarvariabledatatypes.Inmostlanguages,youhavesomemeansofrepresentingstringsandintegers,forexample.Themaximumandminimumsizeofanintegermightdependonthelanguage,butthebasicdatatypeisthesame.Maintainingallthisfunctionalityformultiplelanguagesrequiresalotofwork.Whykeepreinventingthewheel?Wouldntitbeeasiertocreateallthisfunctionalityonceanduseitforeverylanguage?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.UnderstandingNamespacesAsyoumightguess,the.NETframeworkishuge.Itcontainsthousandsofclasses(over3,400).Fortunately,theclassesarenotsimplyjumbledtogether.Theclassesofthe.NETframeworkareorganizedintoahierarchyofnamespaces.ASPClassicNoteInpreviousversionsofActiveServerPages,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.FileSystem.IOreferstothenamespace,andFilereferstotheparticularclass.NOTEYoucanviewallthenamespacesofthestandardclassesinthe.NETFrameworkClassLibrarybyviewingtheReferenceDocumentationforthe.NETFramework.StandardASP.NETNamespacesTheclassescontainedinaselectnumberofnamespacesareavailableinyourASP.NETpagesbydefault.(Youmustexplicitlyimportothernamespaces.)ThesedefaultnamespacescontainclassesthatyouusemostofteninyourASP.NETapplications:SystemContainsallthebasedatatypesandotherusefulclassessuchasthoserelatedtogeneratingrandomnumbersandworkingwithdatesandtimes.System.CollectionsContainsclassesforworkingwithstandardcollectiontypessuchashashtables,andarraylists.System.Collections.SpecializedContainsclassesthatrepresentspecializedcollectionssuchaslinkedlistsandstringcollections.System.ConfigurationContainsclassesforworkingwithconfigurationfiles(Web.configfiles).System.TextContainsclassesforencoding,decoding,andmanipulatingthecontentsofstrings.System.Text.RegularExpressionsContainsclassesforperformingregularexpressionmatchandreplaceoperations.System.WebContainsthebasicclassesforworkingwiththeWorldWideWeb,includingclassesforrepresentingbrowserrequestsandserverresponses.System.Web.CachingContainsclassesusedforcachingthecontentofpagesandclassesforperformingcustomcachingoperations.System.Web.SecurityContainsclassesforimplementingauthenticationandauthorizationsuchasFormsandPassportauthentication.System.Web.SessionStateContainsclassesforimplementingsessionstate.System.Web.UIContainsthebasicclassesusedinbuildingtheuserinterfaceofASP.NETpages.System.Web.UI.HTMLControlsContainstheclassesfortheHTMLcontrols.System.Web.UI.WebControlsContainstheclassesfortheWebcontrols.NETFramework-CompatibleLanguagesForpurposesofthisbook,youwillwritetheapplicationlogicforyourASP.NETpagesusingVisualBasicasyourprogramminglanguage.ItisthedefaultlanguageforASP.NETpages.AlthoughyousticktoVisualBasicinthisbook,youalsoneedtounderstandthatyoucancreateASP.NETpagesbyusinganylanguagethatsupportsthe.NETCommonLanguageRuntime.Outofthebox,thisincludesC#,JScript.NET,andtheManagedExtensionstoC+.NOTETheCDincludedwiththisbookcontainsC#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.NETpageisntcompiledintonativemachinecodeuntilitisactuallyrequestedbyabrowser.Atthatpoint,theclassfilecontainedintheTemporaryASP.NETFilesdirectoryiscompiledwiththe.NETframeworkJustinTime(JIT)compilerandexecuted.Themagicalaspectofthiswholeprocessisthatithappensautomaticallyinthebackground.AllyouhavetodoiscreateatextfilewiththesourcecodeforyourASP.NETpage,andthe.NETframeworkhandlesallthehardworkofconvertingitintocompiledcodeforyou.ASPCLASSICNOTEWhataboutVBScript?BeforeASP.NET,VBScriptwasthemostpopularlanguagefordevelopingActiveServerPages.ASP.NETdoesnotsupportVBScript,andthisisgoodnews.VisualBasicisasupersetofVBScript,whichmeansthatVisualBasichasallthefunctionalityofVBScriptandmore.So,youhavearichersetoffunctionsandstatementswithVisualBasic.Furthermore,unlikeVBScript,VisualBasicisacompiledlanguage.ThismeansthatifyouuseVisualBasictorewritethesamecodethatyouwrotewithVBScript,youcangetbetterperformance.IfyouhaveworkedonlywithVBScriptandnotVisualBasicinthepast,dontworry.SinceVBScriptissocloselyrelatedtoVisualBasic,youllfinditeasytomakethetransitionbetweenthetwolanguages.NOTEMicrosoftincludesaninterestingtoolnamedtheILDisassembler(ILDASM)withthe.NETframework.YoucanusethistooltoviewthedisassembledcodeforanyoftheASP.NETclassesintheTemporaryASP.NETFilesdirectory.Itlistsallthemethodsandpropertiesoftheclassandenablesyoutoviewtheintermediate-levelcode.ThistoolalsoworkswithalltheASP.NETcontrolsdiscussedinthischapter.Forexample,youcanusetheILDisassemblertoviewtheintermediate-levelcodefortheTextBoxcontrol(locatedinafilenamedSystem.Web.dll).IntroducingASP.NETControlsASP.NETcontrolsprovidethedynamicandinteractiveportionsoftheuserinterfaceforyourWebapplication.ThecontrolsrenderthecontentthattheusersofyourWebsiteactuallyseeandinteractwith.Forexample,youcanusecontrolstocreateHTMLformelements,interactivecalendars,androtatingbanneradvertisements.ASP.NETcontrolscoexistpeacefullywithHTMLcontent.Typically,youcreatethestaticareasofyourWebpageswithnormalHTMLcontentandcreatethedynamicorinteractiveportionswithASP.NETcontrols.ThebestwaytounderstandhowASP.NETcontrolsworkinanHTMLpageistolookatasimpleWebFormsPage.AddingApplicationLogictoanASP.NETPageThesecondbuildingblockofanASP.NETpageistheapplicationlogic,whichistheactualprogrammingcodeinthepage.Youaddapplicationlogictoapagetohandlebothcontrolandpageevents.IfauserclicksaButtoncontrolwithinanHTMLform,forexample,theButtoncontrolraisesanevent(theClickevent).Typically,youwanttoaddcodetothepagethatdoessomethinginresponsetothisevent.Forexample,whensomeoneclickstheButtoncontrol,youmightwanttosavetheformdatatoafileordatabase.Controlsarenottheonlythingsthatcanraiseevents.AnASP.NETpageitselfraisesseveraleventseverytimeitisrequested.Forexample,wheneveryourequestapage,thepagesLoadeventistriggered.YoucanaddapplicationlogictothepagethatexecuteswhenevertheLoadeventoccurs.2.BuildingFormswithWebServerControlsBuildingSmartFormsYouuseseveralofthebasicWebcontrolstorepresentstandardHTMLformelementssuchasradiobuttons,textboxes,andlistboxes.YoucanusethesecontrolsinyourASP.NETpagestocreatetheuserinterfaceforyourWebapplication.ThefollowingsectionsprovidedetailedoverviewsandprogrammingsamplesforeachoftheseWebcontrols.ControllingPageNavigationInthefollowingsections,youlearnhowtocontrolhowausermovesfromoneASP.NETpagetoanother.First,youlearnhowtosubmitanHTMLformtoanotherpageandretrieveforminformation.Next,youlearnhowtousetheRedirect()methodtoautomaticallytransferausertoanewpage.Finally,youlearnhowtolinkpagestogetherwiththeHyperLinkcontrol.ApplyingFormattingtoControlsInthefollowingsections,youlearnhowtomakemoreattractiveWebforms.First,youlookatanoverviewoftheformattingpropertiescommontoallWebcontrols;theyaretheformattingpropertiesofthebasecontrolclass.Next,youlearnhowtoapplyCascadingStyleSheetstylesandclassestoWebcontrols.3.PerformingFormValidationwithValidationControlsUsingClient-sideValidationTraditionally,Webdevelopershavefacedatoughchoicewhenaddingformvalidationlogictotheirpages.Youcanaddformvalidationroutinestoyourserver-sidecode,oryoucanaddthevalidationroutinestoyourclient-sidecode.Theadvantageofwritingvalidationlogicinclient-sidecodeisthatyoucanprovideinstantfeedbacktoyourusers.Forexample,ifauserneglectstoenteravalueinarequiredformfield,youcaninstantlydisplayanerrormessagewithoutrequiringaroundtripbacktotheserver.Peoplereallylikeclient-sidevalidation.Itlooksgreatandcreatesabetteroveralluserexperience.Theproblem,however,isthatitdoesnotworkwithallbrowsers.NotallbrowserssupportJavaScript,anddifferentversionsofbrowserssupportdifferentversionsofJavaScript,soclient-sidevalidationisneverguaranteedtowork.Forthisreason,inthepast,manydevelopersdecidedtoaddalltheirformvalidationlogicexclusivelytoserver-sidecode.Becauseserver-sidecodefunctionscorrectlywithanybrowser,thiscourseofactionwassafer.Fortunately,theValidationcontrolsdiscussedinthischapterdonotforceyoutomakethisdifficultchoice.TheValidationcontrolsautomaticallygeneratebothclient-sideandserver-sidecode.IfabrowseriscapableofsupportingJavaScript,client-sidevalidationscriptsareautomaticallysenttothebrowser.IfabrowserisincapableofsupportingJavaScript,thevalidationroutinesareautomaticallyimplementedinserver-sidecode.Youshouldbewarned,however,thatclient-sidevalidationworksonlywithMicrosoftInternetExplorerversion4.0andhigher.Inparticular,theclient-sidescriptsdiscussedinthischapterdonotworkwithanyversionofNetscapeNavigator.RequiringFields:TheRequiredFieldValidatorControlYouuseRequiredFieldValidatorinaWebformtocheckwhetheracontrolhasavalue.Typically,youusethiscontrolwithaTextBoxcontrol.However,nothingiswrongwithusingRequiredFieldValidatorwithotherinputcontrolssuchasRadioButtonList.ValidatingExpressions:TheRegularExpressionValidatorControlYoucanuseRegularExpressionValidatortomatchthevalueenteredintoaformfieldtoaregularexpression.Youcanusethiscontroltocheckwhetherauserhasentered,forexample,avalide-mailaddress,telephonenumber,orusernameorpassword.Samplesofhowtousearegularexpressiontoperformallthesevalidationtasksareprovidedinthefollowingsections.ComparingValues:TheCompareValidatorControlTheCompareValidatorcontrolperformscomparisonsbetweenthedataenteredintoaformfieldandanothervalue.Theothervaluecanbeafixedvalue,suchasaparticularnumber,oravalueenteredintoanothercontrol.SummarizingErrors:TheValidationSummaryControlImaginethatyouhaveaformwith50formfields.IfyouuseonlytheValidationcontrolsdiscussedintheprevioussectionsofthischaptertodisplayerrors,seeinganerrormessageonthepagemightbedifficult.Forexample,youmighthavetoscrolldowntothe48thformfieldtofindtheerrormessage.Fortunately,MicrosoftincludesaValidationSummarycontrolwiththeValidationcontrols.Youcanusethiscontroltosummarizealltheerrorsatthetopofapage,orwhereverelseyouwant.4.AdvancedControlProgrammingWorkingwithViewStateBydefault,almostallASP.NETcontrolsretainthevaluesoftheirpropertiesbetweenformposts.Forexample,ifyouassigntexttoaLabelcontrolandsubmittheform,whenthepageisrenderedagain,thecontentsoftheLabelcontrolarepreserved.Themagicofviewstateisthatitdoesnotdependonanyspecialserverorbrowserproperties.Inparticular,itdoesnotdependoncookies,sessionvariables,orapplicationvariables.ViewstateisimplementedwithahiddenformfieldcalledVIEWSTATEthatisautomaticallycreatedineveryWebFormsPage.Whenusedwisely,viewstatecanhaveadramaticandpositiveeffectontheperformanceofyourWebsite.Forexample,ifyoudisplaydatabasedatainacontrolthathasviewstateenabled,youdonothavetoreturntothedatabaseeachtimethepageispostedbacktotheserver.Youcanautomaticallypreservethedatawithinthepagesviewstatebetweenformposts.DisplayingandHidingContentImaginethatyouarecreatingaformwithanoptionalsection.Forexample,imaginethatyouarecreatinganonlinetaxform,andyouwanttodisplayorhideasectionthatcontainsquestionsthatapplyonlytomarriedtaxfilers.Or,imaginethatyouwanttoaddanadditionalhelpbuttontothetaxform.Youmightwanttohideordisplaydetailedinstructionsforcompletingformquestionsdependingonauserspreferences.Finally,imaginethatyouwanttobreakthetaxformintomultiplepagessothatapersonviewsonlyonepartofthetaxformatatime.Inthefollowingsections,youlearnaboutthepropertiesthatyoucanusetohideanddisplaycontrolsinaform.YoulearnhowtousetheVisibleandEnabledpropertieswithindividualcontrolsandgroupsofcontrolstohideanddisplaypagecontent.UsingtheVisibleandEnabledPropertiesEverycontrol,includingbothHTMLandWebcontrols,hasaVisiblepropertythatdetermineswhetherthecontrolisrendered.WhenacontrolsVisiblepropertyhasthevalueFalse,thecontrolisnotdisplayedonthepage;thecontrolisnotprocessedforeitherpre-renderingorrendering.Webcontrols(butnoteveryHTMLcontrol)haveanadditionalpropertynamedEnabled.WhenEnabledhasthevalueFalseandyouareusingInternetExplorerversion4.0orhigher,thecontrolappearsghostedandnolongerfunctions.Whenusedwithotherbrowsers,suchasNetscapeNavigator,thecontrolmightnotappearghosted,butitdoesnotfunction.DisablingViewStateIncertaincircumstances,youmightwanttodisableviewstateforanindividualcontrolorforanASP.NETpageasawhole.Forexample,youmighthaveacontrolthatcontainsalotofdata(imagineaRadioButtonListcontrolwith1,000options).Youmightnotwanttoloadthedataintothehidden_VIEWSTATEformfieldifyouareworriedthattheformdatawouldsignificantlyslowdowntherenderingofthepage.UsingRichControlsInthefollowingsections,youlearnhowtousethreeofthemorefeature-richcontrolsintheASP.NETframework.YoulearnhowtousetheCalendarcontroltodisplayinteractivecalendars,theAdRotatorcontroltodisplayrotatingbanneradvertisements,andtheHTMLInputFilecontroltoacceptfileuploads.McDonald,ZipuzitatheAdvancedASP.NET3.5Programming(2ndEdition)外文翻译ASP.NET技术1.构建ASP.NET页面ASP.NET和ASP.NET结构ASP.NET是微软.NETframework整体的一部分,它包含一组大量的编程用的类，满足各种编程需要。在下列的二个部分中,你如何学会ASP.NET很适合的放在.NETframework,和学会能在你的ASP.NET页面中使用语言。.NET类库假想你是微软。假想你必须支持大量的编程语言-比如VisualBasic、C#和C+.这些编程语言的很多功能具有重叠性。举例来说，对于每一种语言，你必须包括存取文件系统、与数据库协同工作和操作字符串的方法。此外，这些语言包含相似的编程构造。每种语言,举例来说，都能够使用循环语句和条件语句。即使用VisualBasic写的条件语句的语法不与用C+写的不一样,程序的功能也是相同的。最后，大多数的编程语言有相似的数据变量类型。以大多数的语言，你有设定字符串类型和整型数据类型的方法。举例来说，整型数据最大值和最小值可能依赖语言的种类，但是基本的数据类型是相同的。对于多种语言来说维持这一功能需要很大的工作量。为什么继续再创轮子?对所有的语言创建这种功能一次，然后把这个功能用在每一种语言中岂不是更容易。.NET类库不完全是那样。它含有大量的满足编程需要的类。举例来说，.NET类库包含处理数据库访问的类和文件协同工作，操作文本和生成图像。除此之外，它包含更多特殊的类用在正则表达式和处理Web协议。.NETframework，此外包含支持所有的基本变量数据类型的类，比如：字符串、整型、字节型、字符型和数组。最重要地,写这一本书的目的,.NET类库包含构建的ASP.NET页面的类。然而你需要了解当你构建.NET页面的时候能够访问.NETframework的任意类。理解命名空间正如你猜测的,.NETframework是庞大的。它包含数以千计的类(超过3,400)。幸运地，类不是简单的堆在一起。.NETframework的类被组织成有层次结构的命名空间。ASPClassicNote在先前的ASP中，你仅仅能够访问五个标准类。相比之下ASP.NET提供超过3,400个类!一个命名空间包含一组逻辑的类。举例来说，涉及到与文件系统协同工作的类就集合在System.IO命名空间中。命名空间被组织成一个层次结构(一棵逻辑树)。树根就是SYSTEM命名空间。这个命名空间包含基本的数据类型的所有的类,例如：字符串、数组，还包含提供随机数字和日期的类。你通过完整的类的命名空间能唯一识别任何的类在.NETframework中的位置。举例来说,指定找到一个theFileclass类，按如下操:System.IO.文件System.IO指命名空间，而文件指定特定的类。提示你能够浏览.NETFramework所有的标准类的命名空间。通过.NETFramework的参考文档可以浏览类库。标准的ASP.NET命名空间在默认情况下，在你的ASP.NET页面中，类被包含在一个选定的命名空间中这些默认的命名空间使你在ASP.NET中最常用到的。System命名空间-包含所有的基本数据类型和其他有用的类，例如：那些关于产生随机数字和日期的类。System.Collections命名空间-包含的类是标准的集合类，例如：哈希表，数组列表。System.Collections.Specialized命名空间-包含特殊的集合类，例如：连接列表和字符串集合。System.Configuration命名空间-包括Web.configfiles类。System.Text命名空间-包含编码，解码和操作字符串内容的类。System.Text.RegularExpressions命名空间-包含的是匹配正则表达式和替代操作类。System.Web命名空间-工作在万维网方面包含的是浏览器请求和服务器响应的类。System.Web.Caching命名空间-包含页面缓冲内容和自定义缓冲操作的类。System.Web.Security命名空间-包含执行验证和授权，例如：窗体和密码验证的类。System.Web.SessionState命名空间-包含执行保存状态的类。System.Web.UI命名空间-包含构建ASP.NET页面的用户接口的类。System.Web.UI.HTMLControls命名空间-包含HTML控件的类。System.Web.UI.WebControls命名空间-包含Web控件的类。.NETFramework-可用的语言这一本书的目的,你将会为以VisualBasic作为你的编程语言来完成你的ASP.NET页写程序编写。它是ASP.NET页面的默认语言。虽然你在这一本书中一直用VisualBasic,但是，你也需要了解用其它的支持公共语言库的语言创建ASP.NET页面。除此之外，这包括C#,JScript.NET和C+。提示本书所含的光碟包含C#源代码。除微软之外的公司产生的几十个其他的语言已经能够和.NETframework兼容。这些其他的语言的一些例子包括Python、SmallTalk、Eiffel和COBOL。这就意味着假如你真的想,你可以使用COBOL写ASP.NET页面。不管你使用什么语言开发ASP.NET页面，你需要明白ASP.NET在执行前必须编译，这就意味着ASP.NET执行速度非常快。你第一次请求ASP.NET页面,页面被编译成一个.NET类,这个类文件被保存在一个特殊的目录下这个目录的名字叫TemporaryAS