Beginning ASP.NET 3.5: In C# and VB

1.3. An Introduction to ASP.NET 3.5

When you type a web address like www.wrox.com in your web browser and press Enter, the browser sends a request to the web server at that address. This is done through HTTP, the HyperText Transfer Protocol. HTTP is the protocol by which web browsers and web servers communicate. When you send the address, you send a request to the server. When the server is active and the request is valid, the server accepts the request, processes it, and then sends the response back to the client browser. The relationship between the request and response is shown in Figure 1-7.

For simple, static files, like HTML files or images, the web server simply reads in the file from its local hard drive and sends it to the browser. However, for dynamic files, such as ASPX pages, this is obviously not good enough. If the web server were to send the ASPX file directly to the browser as a text file, you wouldn't have seen the current date and time in the browser, but instead you would have seen the actual code (<%= DateTime.Now.ToString() %>). So, instead of sending the file directly, the web server hands over the request to another piece of software that is able to process the page. This is done with a concept called Application Mapping or Handler Mapping, where an extension of a file (.aspx in this example) is mapped to an application that is capable of handling it. In the case of an .aspx page, the request is eventually handled and processed by the ASP.NET runtime, part ...