ASP.NET教程之怎样在vs.net中使用UML来建模(转自MSDN...

今天去面试，被问到C#中的new关键字，看了那么多的书对new关键字还是有一定认识，回来又把new复习了一遍，发现了许多以前还不知道的细节。VisuallyModelSoftwareApplications
Note:SomefeaturesmaynotbeofferedinthepubliclyavailableVisualStudio.NETBeta2.
Customersbuildingcomplexdistributedapplicationsfacethechallengeofsuccessfullycommunicatingapplicationarchitectureandrequirementsacrossabroadrangeofteammembers.ThischallengecompoundsaswemoveintotheworldoflooselycoupledXMLWebservices.Itiscommonknowledgethatthepresentationofconceptsandinformationinmultipleformats―visual,spoken,written―enhancespeoplesabilitytounderstandmessagesquicklyandaccurately.Takingthismultiple-formatapproachtocommunicating,VisualStudio.NEThelpsfosterteamcoordinationandproductivitybyprovidingarichsetofvisualmodelingtoolsforspecifyingapplicationarchitectureandrequirements.

AnIndustry-StandardApproach
VisualStudio.NETdeliverssupportforafullrangeofdesignandmodelingactivities,includingfreeformdiagrammingcapabilitiesaswellasasetofindustry-standardUnifiedModelingLanguage(UML)diagrams.UMLisanotationforvisuallydescribingandinterpretingthepieces,relationships,andactionsthatcompriseasoftwareapplication.

WiththeVisualStudio.NETmodelingfeatures,userscancreatesophisticateddiagramstospecifytheirapplicationarchitectureandbusinessrequirements,andcancommunicatetheseacrosstheirteams.Businessanalysts,architects,developers―andotherswhowanttoperformanalysisanddesigntaskstoenhancecommunicationandincreasetheproductivityoftheirdevelopmentteams―cantakeadvantageofthesenewcapabilities.ThefollowingscenariodemonstrateshowthestructureofaparticularsoftwaresystemcanbevisualizedandmoreeffectivelycommunicatedbyusingsoftwaremodelscreatedinVisualStudio.NET.

ApplicationScenario:ACarRentalSoftwareSystem
ThisscenariodiscusseshowtheeightUMLdiagramtypesmightbeusedtomodelacarrentalagencyssoftwaresystem.Beginningwiththreesimpleusecases,theexamplescapturethecoreprocessesinthesystem.

UseCaseDiagram
Ausecasespecifiesaninteractionbetweenauserandthesysteminwhichtheuserisabletoachieveagoal.Atypicalsoftwaresystemmightincludehundredsofsimpleusecases.Someusecasesapplicabletotherentalagencyssystemare:

Customerreservescar
Beforeobtainingacar,acustomermustmakeareservation.Thecustomercontactstherentalagencyandmakesarequest.Theagencyacceptsordeclinestherequestbasedonanumberofcriteria,suchastheavailabilityofcarsorthecustomersrentalhistory.Ifthereservationisaccepted,theagencycompletesaformcontainingcustomerdetails.Paymentofadepositcompletesthereservation.
Customerpicksupcar
Whenthecustomerarrivesattheagency,therentalagencyallocatesthemodelofcarrequestedbythecustomer,dependingoncurrentstocklevels.Afterpayingthefullfee,thecustomerreceivesthecar.
Customerreturnscar
Thecustomerreturnsthecartotheagencyonthedayspecifiedintherentalagreement.
Thefollowingimagedepictstheuse-casediagramforthesethreeusecases.


Figure1.Asimpleusecasediagram

StaticStructure(Class)Diagram
Thenexttaskistoclassifytheobjectsinvolvedandtheirrelationships.Examiningusecaseshelpsidentifyclasses.Classesofobjectsaremodeledusingstaticstructure,orclass,diagramsthatshowtheoverallstructureofthesystem,aswellasrelationalandbehavioralproperties.

Inaclassdiagram,theobjectsinvolvedinthecarrentalsystemaregroupedintoclasses.Eachclasscontainsanamesectionandanattributesection.Someclassesalsoincludeanoperationssection,whichspecifieshowobjectswithinthatclassmaybehave.

IntheCustomerclass,attributesincludename,telephonenumber,driverslicensenumber,andaddress.Thedateofbirthisrequiredtodeterminethatthecustomermeetstheminimumagerequirementtorentavehicle.TheCustomerclassalsostoresoperations,suchasreservations.

Classdiagramssupportinheritance.Inthefollowingfigure,forexample,theMechanicandRentalAgentclassesinheritattributes,suchasnameandaddress,fromtheEmployeeclass.


Figure2.Astaticstructure,orclass,diagram

SequenceDiagram
Asequencediagramprovidesadetailedviewofausecase.Itshowsaninteractionarrangedinasequenceovertime,andhelpstodocumenttheflowoflogicwithintheapplication.Theparticipantsareshowninthecontextofthemessagesthatpassbetweenthem.Inacomprehensivesoftwaresystem,thesequencediagramcanbequitedetailed,andcanincludethousandsofmessages.

Supposethatacustomerwantstoreserveacar.Therentalagentmustfirstcheckthecustomersrecordstoensurethatthecustomermaydoso.Ifthecustomerhasrentedacarfromthecompanybefore,hisorherrentalhistorywillalreadyberecorded,andtheagentneedonlyensurethatallprevioustransactionsransmoothly.Forexample,theagentcanconfirmthatthecustomerspreviousrentalcarswerereturnedontime.Oncethecustomersrentalstatusisapproved,therentalagentcanapprovethecarrentalreservation.Thisprocesscanberepresentedinasequencediagram,asshowninthefigurebelow.


Figure3.Asequencediagram

CollaborationDiagram
Acollaborationdiagramisanothertypeofinteractiondiagram.Likeasequencediagram,itshowshowagroupofobjectsinausecaseworkwithoneanother.Eachmessageisnumberedtodocumenttheorderinwhichitoccurs.


Figure4.Acollaborationdiagram

StatechartDiagram
Anobjectsstateisdefinedasitsattributesataparticularmoment.Objectsmovethroughvariousstatesastheyareinfluencedbyoutsidestimuli.Thestatechartdiagrammapsthesestates,aswellasthetriggeringeventsthatcausetheobjecttobeinaparticularstate.Forexample,inourrentalsystem,theobjectisacar.Asacarmovesthroughtherentalsystem,itsmanystatesproduceacomplexbutilluminatingdiagram.Forexample,itisfirstaddedtothefleet.ItremainsinthestateInStockuntilitisrented.Afterrenting,thecarisreturnedtothefleetandtotheInStockstate.Atvarioustimesinitscommerciallife,thecarmayrequirerepairs(InService).Whenthecarreachestheendofitsusefulness,itiseithersoldorscrappedtomakewayforanewvehicle.


Figure5.Astatechartdiagram

ActivityDiagram
Anactivitydiagramdisplaysthelogicthatoccursinresponsetointernallygeneratedactions.Anactivitydiagramrelatestoaspecificclassorusecase,andshowsthestepsinvolvedincarryingoutaparticularoperation.


Figure6.Anactivitydiagram

ComponentDiagram
Acomponentdiagramshowshowvarioussoftwaresubsystemsmakeuptheoverallstructureofthesystem,whichisbuiltonacentralizeddatabasethatcontainspastrentalrecords,cardetails,servicerecords,andcustomerandemployeedetails.Itiscriticalthatthisdatabecentralizedinonedatabase,becausestocklevelsvarybythehourandallpartiesmusthaveup-to-theminuteinformation.Keepingthedatacurrentrequiresreal-timeinformationupdatesbyallparties.ThesoftwaresubsystemsforthisexampleincludeCarRecords,ServiceRecords,SalesRecords,CustomerRecords,andEmployeeRecords.


Figure7.Acomponentdiagram

DeploymentDiagram
Adeploymentdiagramshowshowthehardwareandsoftwareinthesystemareconfigured.Therentalagencyneedsaclient/serversystemwithacentraldatabaseofrecordsthatthestaffcanaccess.Rentalagentsneedaccesstothedataonvehicleavailability.Meanwhile,mechanicsneedtobeabletoflagaparticularcarasbeingintheInServicestate.


Figure8.Adeploymentdiagram

FreeformModeling
ManycustomersalsowanttheabilitytoaddothergraphicalelementstotheUMLdiagramsintheirapplicationmodels.VisualStudio.NETenablesfreeformmodeling,suchasflowchartsandothernon-semanticdiagrams,aswellastheabilitytoembedanyimagewithinamodel.Thisprovidescustomerswithadditionalflexibilityincommunicatingtheirapplicationarchitectureandfunctionality.

Summary
Duringtheapplicationlifecycle,manypeopleofvaryingtechnicalbackgroundsneedtointeractandcommunicatetosuccessfullyaccomplishthecommongoalofcreatinganewapplication.VisualStudio.NETprovideskeyfeatures―industrystandardsoftwaremodelingandrichfreeformdiagrammingcapabilities―forspecifyingandcommunicatingarchitecture.Customerswhousethesefeatureswillbenefitthroughmoreeffectivecommunicationwithintheirdevelopmentteams,whichwillincreasetheefficiencyofdevelopersandthesuccessrateofsoftwareprojectsintheirorganizations.
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也不知道，我同学昨天说数据挖掘很好。

ASP在执行的时候，是由IIS调用程序引擎，解释执行嵌在HTML中的ASP代码，最终将结果和原来的HTML一同送往客户端。

由于CGI程序每响应一个客户就会打开一个新的进程，所以，当有多个用户同时进行CGI请求的时候，服务器就会打开多个进程，这样就加重了服务器的负担，使服务器的执行效率变得越来越低下。

但是目前在CGI中使用的最为广泛的是Perl语言。所以，狭义上所指的CGI程序一般都是指Perl程序，一般CGI程序的后缀都是.pl或者.cgi。

ASP（ActiveServerPages）是Microsfot公司1996年11月推出的WEB应用程序开发技术，它既不是一种程序语言，也不是一种开发工具，而是一种技术框架，不须使用微软的产品就能编写它的代码。

比如封装性、继承性、多态性等等，这就解决了刚才谈到的ASP的那些弱点。封装性使得代码逻辑清晰，易于管理，并且应用到ASP.Net上就可以使业务逻辑和Html页面分离，这样无论页面原型如何改变。

可以通过在现有ASP应用程序中逐渐添加ASP.NET功能，随时增强ASP应用程序的功能。ASP.NET是一个已编译的、基于.NET的环境，可以用任何与.NET兼容的语言（包括VisualBasic.NET、C#和JScript.NET.）创作应用程序。另外，任何ASP.NET应用程序都可以使用整个.NETFramework。开发人员可以方便地获得这些技术的优点，其中包括托管的公共语言运行库环境、类型安全、继承等等。

通过这次激烈的讨论，我从大家身上学到了太多，开阔了眼界，不管是支持我的还是骂我的，都感谢你们。

虽然在形式上JSP和ASP或PHP看上去很相似——都可以被内嵌在HTML代码中。但是，它的执行方式和ASP或PHP完全不同。在JSP被执行的时候，JSP文件被JSP解释器（JSPParser）转换成Servlet代码，然后Servlet代码被Java编译器编译成.class字节文件，这样就由生成的Servlet来对客户端应答。所以，JSP可以看做是Servlet的脚本语言（ScriptLanguage）版。

网页从开始简单的hmtl到复杂的服务语言，走过了10多个年头，各种技术层出不穷，单个的主流技术也在不断翻新的版本，现在分析下各种语言的区别、优势、劣势、开发注意事项！