ASP NET入门C#版毕业论文外文文献翻译.docx

1、D 科技译文Beginning ASP.NET 2.0 in C# ASP (Active Server Pages) is a relatively new technology thats alreadyleapt through several stages of evolution. It was introduced about seven years装ago as an easy way to add dynamic content to ordinary web pages. Since then,its grown into something much more ambiti

2、ous: a platform for creatingadvanced web applications, including merce shops, data.driven portal sites,and just about anything else you can find on the Internet.ASP.NET 2.0 is thelatest version of ASP, and it represents the most dramatic change yet. WithASP.NET, developers no longer need to paste to

3、gether a jumble of HTML andscript code in order to program the Web. Instead, you can create full.scale web订applications using nothing but code and a design tool such as Visual Studio 2008The cost of all this innovation is the learning curve. Not only doyou need tolearn how to use an advanced design

4、tool (Visual Studio) and a toolkit of objects(the .NET Framework), you also need to master a programming language suchas C#.The Internet began in the late 1960s as an experiment. Its goal was tocreate a truly resilient information networkone that could withstand the loss of线several computers without

5、 preventing the others from communicating. Drivenby potential disaster scenarios (such as nuclear attack), the U.S. Department ofDefense provided the initial funding. The early Internet was mostly limited toeducational institutions and defense contractors. It flourished as a tool foracademiccollabor

6、ation,allowingresearchersacrosstheglobetoshareinformation. In the early 1990s, modems were created that could work over existing phone lines, and the Internet began to open up to commercial users. In1993, the first HTML browser was created, and the Internet revolution began. Itwould be difficult to

7、describe early websites as web applications. Instead, thefirst generation of websites often looked more like brochures, consisting mostlyof fixed HTML pages that needed to be updated by hand. Basic HTML page is alittle like a word.processing documentit contains formatted content that can bedisplayed

8、 on your computer, but it doesnt actually do anything. The following装example shows HTML at its simplest, with a document that contains a headingand single line of text: An HTML document has two types of content: the textand the tags that tell the browser how to format it. The tags are easilyrecogniz

9、able, because they occur inside angled brackets (). HTML definestags for different levels of headings, paragraphs, hyperlinks, italic and boldformatting, horizontal lines, and so on. For example, Some Text tellsthe browser to display Some Text in the Heading 1 style, which uses a large,订bold font. F

10、igure 1.1 shows the simple HTML page in a browser.HTML 2.0introduced the first seed of web programming with a technology called HTMLforms. HTML forms expand HTML so that it includes not only formatting tagsbut also tags for graphical widgets, or controls. These controls include commoningredients suc

11、h as drop.down lists, text boxes, and buttons. Heres a samplewebpage createdwithHTML form controls:HTML formsallowweb线application developers to design standard input pages. When the user clicks theSubmit button on the page shown in Figure 1.2, all the data in the input controls(in this case, the two

12、 check boxes) is patched together into one long string andsent to the web server. On the server side, a custom application receives andprocesses the data. Amazingly enough, the controls that were created for HTMLforms more than ten years ago are still the basic foundation thatyoull use tobuild dynam

13、ic ASP.NET pages! The difference is the type of application thatruns on the server side. In the past,when the user clicked a button on a formpage, the information might have been e.mailed to a set account or sent to anapplication on the server that used the challenging CGI (Common GatewayInterface)

14、standard. Today, youll work with the much more capable and elegantASP.NET platform. To understand why ASP.NET was created, it helps to装understand the problems of other web development technologies. With theoriginal CGI standard, for example, the web server must launch a completelyseparate instance o

15、f the application for each web request. If the website ispopular, the web server must struggle under the weight of hundreds of separatecopies of the application, eventually becoming a victim of its own successorcounter this problem, Microsoft developed ISAPI (Internet Server ApplicationProgramming I

16、nterface), a higher.level programming model. ISAPI solved the订performance problem but at the cost of significant complexity. Even after ISAPIdevelopers master the tricky C+ programming language, they still lie awake atnight worrying about confounding issues such as multithreading.ISAPIprogramming is

17、 definitely not for the fainthearted. SAPI never really went away.Instead, Microsoft used it to build higher.level develop.mint platforms, such asASP and ASP.NET. Both of these technologies allow developers to program线dynamic web pages without worrying about the low.level implementation details.For

18、that reason, both platforms have become incredibly successful. The originalASP platform garnered a huge audience of nearly one million developers. WhenASP.NET was first released, it generated even more interest as the centerpiece ofthe .NET Frame.work. In fact, ASP.NET 1.0 was enthusiastically put t

19、o work indozens of large.scale commercial websites even when it was only in late beta.Despite having similar underpinnings, ASP and ASP.NET are radically different.ASP isa script.basedprogramming languagethatrequires athoroughunderstanding of HTML and a good deal of painful coding. ASP.NET, on theot

20、her hand, is an object.oriented pro.gamming model that lets you put together aweb page as easily as you would build a Windows application. In many respects,its easier to learn ASP.NET than to master ASP, even though ASP.NET is far装more powerful. At the same time that server.side web development was

21、movingthrough an alphabet soup of technologies, a new type of programming wasgaining popularity. Developers began to experiment with the different ways theycould enhance web pages by embed.ding multimedia and miniature applets builtwith JavaScript, DHTML (Dynamic HTML), and Java code. These client.s

22、idetechnologies dont involve any server processing.Instead, the completeapplication is downloaded to the client browser, which executes it locally. The订greatest problem with client.side technologies is that they arent supportedequally by all browsers and operating systems. One of the reasons that we

23、bdevelopment is so popular in the first place is because web applications dontrequire setup CDs, down.loads, and other tedious (and error.prone) deploymentsteps. Instead, a web application can be used on any computer that has Internetaccess. But when developers use client.side technologies, they enc

24、ounter a few线familiar headaches. Suddenly, cross.browser compatibility becomes a problem.Developers are forced to test their websites with operating systems andbrowsers, and they might even need to distribute browser updates to their clients.In other words, the client.side model sacrifices some of t

25、he most importantbenefits of web development. or that reason, ASP.NET is designed as aserver.side technology. All ASP.NET code executes on the server. When the codeis finished executing, the user receives an ordinary HTML page, which can beviewed in any browser. Figure 1.3 shows the difference betwe

26、en the server.sideand client.side model. These are some other reasons for avoiding client.sideprogramming: Isolation: Client. side code cant access server .side resources. Forexample, a client.side application has no easy way to read a file or interact witha database on the server (at least not with

27、out running into problems with security装and browser compatibility).Security: End users can view client.side code. Andonce malicious users understand how an application works, they can oftentamper with it. me cases, ASP.NET allows you to combine the best of client.sideprogramming with server.side pro

28、gramming. For example, the best ASP.NETcontrols can intelligently detect the features of the client browser. If the browsersupports JavaScript, these controls will return a web page that incorporatesJavaScript for a richer, more responsive user interface. However, no matter what订the capabilities of

29、the browser, your code is always executed on the server. Statelimitations: To ensure optimum performance, the Web is built on statelessprotocols, which means as soon as a page is sent to a user, the connection isclosed and any user.specific information is discarded. ASP includes a sessionstate feature that allows programmers to work around this problem. Usingsession state, a web application can retain temporary