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Web Forms: Web Pages with Server Controls

Web Forms: Web Pages with Server Controls. Objectives. Understand the background of the Internet, and the notions of packet switching and a stateless medium

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Web Forms: Web Pages with Server Controls

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  1. Web Forms: Web Pages with Server Controls

  2. Objectives • Understand the background of the Internet, and the notions of packet switching and a stateless medium • Understand the operating principles of the World Wide Web, especially HTML, Web browser software, HTTP, and the Web’s cataloging scheme and search engines • Understand the features of XML that make it the language of choice for Web-based computer applications • Define and describe ASP.NET Web Forms applications • Understand the basic approach to the construction and deployment of Web Forms applications, distinguishing among HTML elements and client controls, HTML server controls, and Web server controls • Describe the importance of workarounds

  3. The Internet • Started as ARPANET, a creation of the U.S. Department of Defense’s Advanced Research Projects Agency (ARPA) • Original idea • Develop a computer network linking the Defense Department’s research laboratories and the universities performing defense-related research • ARPANET • Nondefense use overshadowed defense-related use • Renamed Internet • MILNET • Introduced in 1983 to assume the defense-related work of ARPANET

  4. The Internet (Continued) • Packet-switched network • Network in which messages are transmitted from node to node in fixed-length message blocks called packets • Individual message divided into sequentially numbered packets • Each packet consists of • Header identifying the origination and destination computers • Date-time stamp • Packet number, followed by packet body • Transmission Control Protocol/Internet Protocol • Principal software supporting end-user machines • Stateless • Internet does not maintain knowledge concerning • The originator, recipient, or contents of messages, nor does it maintain a connection between the originator and the recipient

  5. The World Wide Web • Tim Berners Lee • Introduced the Web in 1989 as a means for sharing information among the world’s nuclear research centers • Hypertext Markup Language (HTML) • Purpose is to describe the presentation of the data, that is, to provide formatting instructions • Markup languages • Inserted into a text document in order to describe the data or provide formatting or processing instructions • Tags are enclosed in angled brackets (< >) • Web Browser Software • Main purpose is to properly interpret the markup language tags in a Web page and render the page on the client computer’s screen • Web browser • Allows any Web page to be displayed, masking and accommodating differences among operating systems, monitors, and graphics software

  6. The World Wide Web (Continued) • Hypertext Transfer Protocol (HTTP) • Hypertext Refers to text that includes a hidden reference (called a hyperlink) to another Web page or Web site • Cataloging Scheme and Search Engines • URL address • Consists of the Internet service, the domain name, the path to the Web page (if necessary), and the title of the Web page (if necessary) • Domain name • Correlates to the Internet Protocol (IP) address of the server • Domain name server (DNS) for a Web server • Usually consists of www, followed by a meaningful domain name, and the top-level domain (TLD) • Search engine • A software program combined with a database

  7. eXtensible Markup Language (XML) • May be the most significant improvement to the World Wide Web in the last decade • Services include the definition of datasets and specification of processing instructions • Foundation technology for implementing XML is Active Server Pages in the .NET Framework (ASP.NET) • Client-based Web applications • Computer programs delivered to a local browser, and executed on the client machine • Include static Web pages, Windows Forms applications distributed to the client machine, and applets executing on the client • Server-based applications • Execute on the server • Include XML documents containing or referencing servlets, applications that run on the server, applications that update a database accessed through the server

  8. ASP.NET Web Forms Applications • Visual Basic 6.0 • Limited support for Web-oriented applications was provided • Visual Basic .NET • Extends both the simplicity and robustness of Visual Basic to the World Wide Web • Visual Basic .NET Web Forms • Allows you to design XML applications that consist of ASP.NET documents materialized in a browser, XML Web services that provide data, and ASP.NET code that executes on the Web server • GUI • Saved as an ASP.NET Web page (.aspx file), translating the graphical design elements into XML • Code Editor • Can be used to write code for a Web page

  9. Web Forms Application Support Files • Global.asax.vb (along with the related Global.asax and Global.asax.resx) • Provides a common structure for all of the code necessary to maintain session state • Styles.css • Provides the cascading style sheet for a Visual Basic .NET Web Forms application • The standard format of any XML cascading style sheet • Web.config • Sets the system configuration for the application • WebApplication1.vsdisco • Serves as a container for links (URLs) to discovery files that describe the XML Web service • Discovery file • Contains the URL of a Web site within which the source code for an XML Web service may be dynamically discovered

  10. WebForm1 - the Web Form Itself • Console applications • Consist only of code, contained in modules • Core of a Windows Forms application • Contained in Windows Forms • Form 1 • Default name for first form • Stored in two files: Form1.vb and Form1.resx • WebForm1 • Default name of first Web form • Stored in three files: WebForm1.aspx, WebForm1.aspx.vb, and WebForm1

  11. Summary of Project Files - Default Names

  12. WebForm1 - the Web Form Itself (Continued) • HTML Elements • Include static text and browser (client) controls that may run client-side script • HTML Server Controls • Some HTML elements can be converted into HTML server controls • Ideally, a Web form should only contain Web server controls and HTML server controls that require server-side code

  13. WebForm1 - the Web Form Itself (Continued) • Web Server Controls • 30 offered by Visual Basic .NET • Some provide functionality tailored to Web-based applications • Web page is rendered in a browser on a client machine, whereas the code is executed on the server • Web form may contain HTML elements, HTML server controls, and Web server control • The Web Forms you create should exhibit well-formed HTML • Deployment of Web Forms Applications • Can be deployed on the same server on which it is developed or on a different machine • Setup project • Prepares the files necessary to install the application

  14. Workarounds • Occur because: • Existing language may not perform some necessary function at all, or completely or efficiently • Programmers often face a programming requirement whose solution is not provided directly by the chosen programming language, or that does not work as advertised

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