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Visual C# 2005 How to Program, 2/e
Visual C# 2005 How to Program, 2/e

© 2006
pages: 1535

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This is the second in a series of four tutorials that introduces ASP.NET 2.0 and Microsoft's Visual Web Developer Express IDE for building Web applications. The Visual Web Developer Express functionality we discuss is also part of the complete Visual Studio 2005. Both Visual Web Developer Express and Visual Studio 2005 were released in November 2005. This series of tutorials is a small part of Chapter 21, ASP.NET, Web Forms and Web Conrols, from our forthcoming book Visual C# 2005 How to Program, 2/e. Chapter 21 is part of a four chapter sequence on XML, ADO.NET, ASP.NET and Web Services in which we discuss each of these technologies and demonstrate how to build substantial, data driven Web applications.

Part 1 of this series provided a brief introduction to ASP.NET, Web Forms and Web controls. This tutorial discusses simple HTTP transactions that enable client/server interactions on the Web. Part 3 overviews multitier application architecture. Part 4 presents a simple Web Form example, analyzes its parts, shows how it executes, and discusses how to build and deploy the Web Form. The tutorials in this series are intended for students and professionals who are already familiar with Visual C# programming.

[Note: This series of tutorials is an excerpt (Sections 21.1-21.4) of Chapter 21, ASP.NET, Web Forms and Web Controls (pp. 1051-1070), from our textbook Visual C# 2005 How to Program, 2/e. These tutorials may refer to other chapters or sections of the book that are not included here. Permission Information: Deitel, Harvey M. and Paul J., Visual C# 2005 How to Program, 2/e 2005. Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.]

21.2   Simple HTTP Transactions
Web application development requires a basic understanding of networking and the World Wide Web. In this section, we discuss the Hypertext Transfer Protocol (HTTP) and what occurs behind the scenes when a browser displays a Web page. HTTP specifies a set of methods and headers that allow clients and servers to interact and exchange information in a uniform and predictable manner.
In its simplest form, a Web page is nothing more than an XHTML document-a plain text file containing markup (i.e., tags) that describe to a Web browser how to display and format the document's information. For example, the XHTML markup
<title>My Web Page</title>
indicates that the browser should display the text between the <title> start tag and the </title> end tag in the browser's title bar. XHTML documents also can contain hypertext data (usually called hyperlinks), which links to different pages or to other parts of the same page. When the user activates a hyperlink (usually by clicking it with the mouse), the requested Web page loads into the user's browser window.
Any XHTML document available for viewing over the Web has a corresponding Uniform Resource Locator (URL). A URL is an address indicating the location of an Internet resource, such as an XHTML document. The URL contains information that directs a browser to the resource that the user wishes to access. Computers that run Web server software make such resources available. When requesting ASP.NET Web applications, the Web server is usually Microsoft Internet Information Services (IIS). As we discuss shortly, it is also possible to test ASP.NET applications using the ASP.NET Development Server built into Visual Web Developer.
Let us examine the components of the URL
The http:// indicates that the resource is to be obtained using the HTTP protocol. The middle portion,, is the server's fully qualified hostname-the name of the computer on which the resource resides. This computer usually is referred to as the host, because it houses and maintains resources. The hostname is translated into an IP address (, which identifies the server in a manner similar to how a telephone number uniquely defines a particular phone line. The hostname is translated into an IP address by a domain name system (DNS) server-a computer that maintains a database of hostnames and their corresponding IP addresses. This translation operation is called a DNS lookup.
Pages in this Tutorial: 1 | 2

Tutorials in This Series:
ASP.NET Tutorial Part 1: Introduction to ASP.NET
ASP.NET Tutorial Part 2: Simple HTTP Transactions (You are here.)
ASP.NET Tutorial Part 3: Multitier Application Architecture
ASP.NET Tutorial Part 4: Creating and Running a Simple Web Form Example

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