《ASP.NET入门C#版-毕业论文外文翻译.docx》由会员分享，可在线阅读，更多相关《ASP.NET入门C#版-毕业论文外文翻译.docx（14页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、Beginning ASP.NET 2.0 in C#ASP (Active Server Pages) is a relatively new technology thats already leapt through several stages of evolution. It was introduced about seven years ago as an easy way to add dynamic content to ordinary web pages. Since then, its grown into something much more ambitious:
2、a platform for creating advanced web applications, including e-commerce shops, data-driven portal sites, and just about anything else you can find on the Internet.ASP.NET 2.0 is the latest version of ASP, and it represents the most dramatic change yet. With ASP.NET, developers no longer need to past
3、e together a jumble of HTML and script code in order to program the Web. Instead, you can create full-scale web applications using nothing but code and a design tool such as Visual Studio 2005. The cost of all this innovation is the learning curve. Not only do you need to learn how to use an advance
4、d design tool (Visual Studio) and a toolkit of objects (the .NET Framework), you also need to master a programming language such as C#.The Internet began in the late 1960s as an experiment. Its goal was to create a truly resilient information networkone that could withstand the loss of several compu
5、ters without preventing the others from communicating. Driven by potential disaster scenarios (such as nuclear attack), the U.S. Department of Defense provided the initial funding. The early Internet was mostly limited to educational institutions and defense contractors. It flourished as a tool for
6、academic collaboration, allowing researchers across the globe to share information. In the early 1990s, modems were created that could work over existing phone lines, and the Internet began to open up to commercial users. In 1993, the first HTML browser was created, and the Internet revolution began
7、. It would be difficult to describe early websites as web applications. Instead, the first generation of websites often looked more like brochures, consisting mostly of fixed HTML pages that needed to be updated by hand. Basic HTML page is a little like a word-processing documentit contains formatte
8、d content that can be displayed on your computer, but it doesnt actually do anything. The following example shows HTML at its simplest, with a document that contains a heading and single line of text: An HTML document has two types of content: the text and the tags that tell the browser how to forma
9、t it. The tags are easily recognizable, because they occur inside angled brackets (). HTML defines tags for different levels of headings, paragraphs, hyperlinks, italic and bold formatting, horizontal lines, and so on. For example, Some Text tells the browser to display Some Text in the Heading 1 st
10、yle, which uses a large, bold font. Figure 1-1 shows the simple HTML page in a browser.HTML 2.0 introduced the first seed of web programming with a technology called HTML forms. HTML forms expand HTML so that it includes not only formatting tags but also tags for graphical widgets, or controls. Thes
11、e controls include common ingredients such as drop-down lists, text boxes, and buttons. Heres a sample web page created with HTML form controls:HTML forms allow web application developers to design standard input pages. When the user clicks the Submit button on the page shown in Figure 1-2, all the
12、data in the input controls (in this case, the two check boxes) is patched together into one long string and sent to the web server. On the server side, a custom application receives and processes the data. Amazingly enough, the controls that were created for HTML forms more than ten years ago are st
13、ill the basic foundation that youll use to build dynamic ASP.NET pages! The difference is the type of application that runs on the server side. In the past, when the user clicked a button on a form page, the information might have been e-mailed to a set account or sent to an application on the serve
14、r that used the challenging CGI (Common Gateway Interface) standard. Today, youll work with the much more capable and elegant ASP.NET platform. To understand why ASP.NET was created, it helps to understand the problems of other web development technologies. With the original CGI standard, for exampl
15、e, the web server must launch a completely separate instance of the application for each web request. If the website is popular, the web server must struggle under the weight of hundreds of separate copies of the application, eventually becoming a victim of its own successor counter this problem, Mi
16、crosoft developed ISAPI (Internet Server Application Programming Interface), a higher-level programming model. ISAPI solved the performance problem but at the cost of significant complexity. Even after ISAPI developers master the tricky C+ programming language, they still lie awake at night worrying
17、 about confounding issues such as multithreading. ISAPI programming is definitely not for the fainthearted. SAPI never really went away. Instead, Microsoft used it to build higher-level develop-mint platforms, such as ASP and ASP.NET. Both of these technologies allow developers to program dynamic we
18、b pages without worrying about the low-level implementation details. For that reason, both platforms have become incredibly successful. The original ASP platform garnered a huge audience of nearly one million developers. When ASP.NET was first released, it generated even more interest as the centerp
19、iece of the .NET Frame-work. In fact, ASP.NET 1.0 was enthusiastically put to work in dozens 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 is a script-based programming language that requires
20、a thorough understanding of HTML and a good deal of painful coding. ASP.NET, on the other hand, is an object-oriented pro-gamming model that lets you put together a web page as easily as you would build a Windows application. In many respects, its easier to learn ASP.NET than to master ASP, even tho
21、ugh ASP.NET is far more powerful. At the same time that server-side web development was moving through an alphabet soup of technologies, a new type of programming was gaining popularity. Developers began to experiment with the different ways they could enhance web pages by embed-ding multimedia and
22、miniature applets built with JavaScript, DHTML (Dynamic HTML), and Java code. These client-side technologies dont involve any server processing. Instead, the complete application is downloaded to the client browser, which executes it locally. The greatest problem with client-side technologies is tha
23、t they arent supported equally by all browsers and operating systems. One of the reasons that web development is so popular in the first place is because web applications dont require setup CDs, down-loads, and other tedious (and error-prone) deployment steps. Instead, a web application can be used
24、on any computer that has Internet access. But when developers use client-side technologies, they encounter a few familiar headaches. Suddenly, cross-browser compatibility becomes a problem. Developers are forced to test their websites with differ-net operating systems and browsers, and they might ev
25、en need to distribute browser updates to their clients. In other words, the client-side model sacrifices some of the most important benefits of web development. or that reason, ASP.NET is designed as a server-side technology. All ASP.NET code executes on the server. When the code is finished executi
26、ng, the user receives an ordinary HTML page, which can be viewed in any browser. Figure 1-3 shows the difference between the server-side and client-side model. These are some other reasons for avoiding client-side programming: Isolation: Client-side code cant access server-side resources. For exampl
27、e, a client-side application has no easy way to read a file or interact with a database on the server (at least not without running into problems with security and browser compatibility).Security: End users can view client-side code. And once malicious users understand how an application works, they
28、 can often tamper with it. me cases, ASP.NET allows you to combine the best of client-side programming with server-side programming. For example, the best ASP.NET controls can intelligently detect the features of the client browser. If the browser supports JavaScript, these controls will return a we
29、b page that incorporates JavaScript for a richer, more responsive user interface. However, no matter what the capabilities of the browser, your code is always executed on the server. State limitations: To ensure optimum performance, the Web is built on stateless protocols, which means as soon as a p
30、age is sent to a user, the connection is closed and any user-specific information is discarded. ASP includes a session state feature that allows programmers to work around this problem. Using session state, a web application can retain temporary information about each client in server memory. Howeve
31、r, session state is useless in scenarios where a website is hosted by several separate web servers. In this scenario, a client might access server B while its session information is trapped on server A and essentially abandoned. ASP.NET corrects this problem by allowing state to be stored in a centr
32、al repository, such as a separate process or a database that all servers can access.ASP.NET deals with these problems (and many more) by introducing a completely new model for web pages. This model is based on a remarkable piece of technology called the NET Framework. You should understand that the
33、.NET Framework is really a cluster of several technologies: The .NET languages: These include C# and VB .NET (Visual Basic .NET), the object-oriented and modernized successor to Visual Basic 6.0; these languages also include Script .NET (a server-side version of JavaScript), J# (a Java clone), and C
34、+ with Managed Extensions. he CLR (Common Language Runtime): The CLR is the engine that executes all .NET programs and provides automatic services for these applications, such as security checking, memory management, and optimization. The .NET Framework class library: The class library collects thou
35、sands of pieces of rebuilt functionality that you can “snap in” to your applications. These features are sometimes organized into technology sets, such as ADO.NET (the technology for creating database applications) and Windows Forms (the technology for creating desktop user interfaces).ASP.NET: This
36、 is the engine that hosts web applications and web services, with almost any feature from the .NET class library. ASP.NET also includes a set of web-specific services.sual Studio: This optional development tool contains a rich set of productivity and debugging features. The Visual Studio setup CDs (
37、or DVD) include the complete .NET Framework, so you wont need to download it separately. Interestingly, C# and VB .NET are actually far more similar than Java and C# or than VB6 and VB .NET. Though the syntax is different, both C# and VB .NET use the .NET class library and are supported by the CLR.
38、In fact, almost any block of C# code can be translated, line by line, into an equivalent block of VB .NET code. An occasional language difference pops up (for example, C# supports a language feature called anonymous methods, while VB .NET doesnt), but for the most part, a developer who has learned o
39、ne .NET language can move quickly and efficiently to anothers short, both C# and VB .NET are elegant, modern languages that are ideal for creating the next generation of web applications.NET 1.0 introduced completely new languages. However, the changes in the .NET 2.0 languages are much more subtle.
40、 Both C# 2005 and VB 2005 add a few new features, but most parts of these languages remain unchanged. As a result, any code written according to version 1.0 of the C# language will work identically with version 2.0. In Chapters 2 and 3, youll sort through the syntax of C# and learn the basics of obj
41、ect-oriented programming. By learning the fundamentals before you start creating simple web pages, youll face less confusion and move more rapidly to advanced topics such as database access and web services. he CLR runs only IL code, which means it has no idea which .NET language you originally used
42、. Notice, however, that the CLR actually performs another compilation stepit takes the IL code and transforms it to native machine language code thats appropriate for the current platform. This step occurs when the application is launched, just before the code is actually executed. In an ASP.NET app
43、lication, these machine-specific files are cached while the web application is running so that they can be reused, ensuring optimum performance. You might wonder why .NET compilers dont compile straight to machine code. The reason is that the machine code depends on several factors, including the CP
44、U. For example, if you create machine code for a computer with an Intel processor, the compiler may be able to use Hyper-Threading to produce enhanced code. This machine-specific version isnt suitable for deployment to other computers, because no guarantee exists that theyre using the same processor
45、. Another welcome change in Visual Studio 2005 is the support for different coding models. While Visual Studio .NET 2003 locked developers into one approach, Visual Studio 2005 supports a range of different coding models, making it a flexible, all-purpose design tool. That means you can choose to pu
46、t your HTML tags and event handling code in the same file or in separate files without compromising your ability to use Visual Studio and benefit from helpful features such as IntelliSense. ASP.NET入门C#版ASP(动态服务器主页)是一种较新的技术,它已经过几个阶段的发展(进化).它是怎么诞生的呢?在七年前,它作为一种简单的方法来往普通网页里添加动态内容。自从那时以后，它的发展势头强劲：作为高级网页程
47、序的开发平台，包括：电子商务网站、基于事件驱动的门户网站和你在网上能看到的其他所有东西。ASP.NET 2.0 是ASP的最新版本,而且拥有最让人激动的更新。在ASP.NET帮助下，在网络编程时，开发者不再把一大堆HTML源码和脚本代码杂乱地放在同一页面上。你可以完全使用代码和工具（Visual Studio 2005）来创建网页程序。这些创新的代价仅仅是多学一些东西。你要学一些高级开发工具（Visual Studio）和工具包（the .NET Framework），而且你需要精通一门编程语言，如C。网络发展的演化因特网是在1960年末在试验中诞生的。它的目标是：建立一个真实的、有弹性的信息
48、网络可以经受的起若干数量的电脑的崩溃，而不至于阻断其他电脑的正常通信。经得起潜在的重大灾难（如核武器攻击）。美国国防部提供了刚开始的研究基金。最早的因特网局限在教育机构和从事国防的单位。它因为作为学术研究的一种工具而繁荣，它让全球的研究人员可以彼此共享信息。到了1990初，伟大的“猫”诞生了，它通过电话线工作，从此，因特网向商业用户打开了大门。在1993年，第一个HTML浏览器诞生了，标志着因特网革命的到来。我们很难把最早的网页称为网页序。第一代的网页看起来更像小册子：主要由固定的HTML页面构成，这些也都需要手动修改。一个简单的HTML页面有点像一个字处理文档它包含了格式化的内容，可以在你的
49、电脑上显示，但是并不完成其他任何功能。上面的就是一个最简单的例子，文档包括头信息和单行文本。一个HTML文档有两种类型的内容：文本和标记（告诉浏览器如何格式化）。这些标记很容易辨认，因为它们总是出现在之间。HTML定义了不同级别的标题、段落、超链接、斜体和粗体格式、水平线等。举个例子：某个文本，告诉浏览器用标题1的格式来显示这个文本，就是用最大的黑体字来显示。图11显示了这个页面在浏览器中的效果。提示：你不需要精通HTML就能进行ASP.NET网页编程，虽然它（HTML）是很有用的。为了快速介绍一下HTML，给大家介绍一个网上的优秀HTML指南。HTML 2.0 首次引入了一个网页编程的新技术，称为HTML表单。HTML表单扩展了HTML的功能，不仅包含了格式化标签，而且包含了窗体小部件或者叫控件。这些控件包含了普通的功能部件，如下拉列表、文本框和按钮。下面是一个由HTML表单控件创建的网页。网页表单允许网页程序设计师设计标准的输入页面。当用户单击图12的提交按钮，所有在输入控件中的数据（在这个例子中是两个复选框）将打包成一个长字符串，接着发送到服务器。在服务器端，一个客户程序接收和处理这些数据。令人惊奇的是:这些为HTML表单创建有超过十年