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Creating a class that implements the IHTTPHandler interface

To create a class that implements the IHTTPHandler interface, complete the following steps:

1.Create an ASP.NET Web Application project by using either C# or Visual Basic.NET.

2.Add a class to the project.

3.In the class that you added, create a class that implements the IHttpHandler interface. Also, implement the ProcessRequest method and the IsReusable property of the IHttpHandler interface.

4.Build the project to create the DLL file for the handler class.

§verb: Indicates the HTTP verb type that the handler services request. This attribute takes a string value, such as verb = "Get" or verb = "Get; Head; Post". If the attribute takes an asterisk (*) as a value, it instructs the HTTP runtime to match on all HTTP verbs.

§path: Indicates the request path, such as /Trial/Sample.aspx, which the

handler is mapped to.

You can also specify any file extension, such as .Rita. But, for this to work, Tip you must map this file extension in IIS. You can do so in the IIS Microsoft

Management Console (MMC).

§type: Indicates the name of the .NET class that contains the HTTP handler code. This attribute takes the value in the following format: [Namespace].[Class].[Assembly name].

Next, you need to add a reference to the DLL file of the handler class. To do so, select Add Reference from the Project menu. This opens the Add Reference dialog box. In this dialog box, click Browse to select the DLL file of the handler.

After you've added the entry for the handler in the Web.config file and added its reference, when you browse the page (whose path is mentioned in the "path" attribute of the <add> tag), you'll notice that the handler automatically handles this request.

Now that you know the general steps, let's implement them to create a custom HTTP handler.

'an object of the HttpBrowserCapabilities class

Dim hBrC As HttpBrowserCapabilities = Context.Request.Browser

'Displaying the name and version of the browser Context.response.Write("<b>Browser capabilities:</b><br>") Context.Response.Write("Name = " & HBrC.Browser & "<br>") Context.Response.Write("Version=" & HBrC.Version & "<br>")

'Using the PhysicalApplicationPath and the

'Applicationpath properties of the Request object to get

'the physical path and the virtual path of the

'application respectively

Dim pPath As String

Dim vPath As String

pPath = Context.Request.PhysicalApplicationPath

vPath = Context.Request.ApplicationPath

'Displaying the virtual and physical path of the

'application

Context.Response.Write("<Br><b>Virtual path of the application:</b><Br>")

Context.Response.Write(vPath & "<br>")

Context.Response.Write("<Br><b>Physical path of the application:</b><Br>")

Context.Response.Write(pPath & "<Br>")

'Using the IsClientConnected property of the Response

'object to determine whether the client is connected to

'the server

Dim connect As Boolean

Dim connectStr As String

connect = Context.Response.IsClientConnected connectStr = connect.ToString

Context.Response.Write("<Br><b>Client connection status:</b><br>") Context.Response.Write(connectStr)

End Sub

'Implementing the IsReusable method of the IHttpHandler

'interface

sent by the client. You also learned about HTTP modules and HTTP handlers. Next, you learned about various interfaces, classes, and built-in objects provided in ASP.NET for creating your own HTTP handlers. Finally, you learned how to create an HTTP handler.

Chapter 17: Understanding Caching

Overview

Usually, Web sites (Web applications) are accessed by multiple users. On certain days, a Web site can experience an extremely low load and, as a result, provide faster access. However, in just a few hours, the load on the site can increase exponentially, resulting in slow access. Slow access is the most common problem that plagues a Web site when it is accessed by a large number of users simultaneously. However, load is not the only reason why a Web site is slow. Other physical aspects affect speed, such as the type of modem, Internet connection, and telephone line. Therefore, it might not be good business sense to invest in high-grade hardware that handles the entire load just to improve the access speed, because the heavy load is only temporary and not constant. It would be better if access speeds could be improved without investing in high-grade hardware. In such a scenario, caching provides a solution.

Caching is a technique wherein frequently used data and Web pages are stored temporarily on local hard disks for later retrieval. This technique improves the access time when multiple users access a Web site simultaneously or a single user accesses a Web site multiple times. Caching allows server-side Web applications to scale better, and improves the overall performance of the Web application. Thus, the ASP.NET code does not need to be executed every time to process the same request from multiple clients or from a single client multiple times. This saves on the CPU cycles at the Web server, resulting in improved response time.

This chapter introduces you to caching. You will also learn the concept of caching page output and caching page data for optimizing the ASP.NET Web applications.

Introduction to Caching

Caching, as a technique for improving system performance, is not a new concept. It has been used successfully in various applications, ranging from relational databases such as Microsoft SQL Server to various operating systems. ASP.NET provides a Web cache to store Web objects.

A Web cache is a temporary storage of Web objects, such as HTML documents, for later retrieval. You can specify the cache location to be on the client or on the server. The different locations where caching can be performed are described as follows:

§Client: To provide improved performance, client applications (like browsers) perform caching by storing data from the Web in temporary files on the hard drive or system memory of users' computers. However, these caches cannot be shared across multiple users. Figure 17-1 demonstates caching at the client side.

Figure 17-1: Client caching

§Dedicated server: Caching can be performed at the server side so that caches can be shared across multiple users on a network. Most administrators use proxy servers, such as Microsoft Proxy Server, to store frequently used Web pages on the hard disk of the proxy server. The proxy server fulfills all the requests for the Web page without sending out the request to the actual Web server over the Internet, resulting in faster access. Figure 17-2 shows caching at the proxy side.

Figure 17-2: Dedicated server caching

Proxy caches are often located near network gateways to reduce the Note bandwidth required over expensive dedicated Internet connections.

These systems serve many users (clients) with cached objects from many servers.

The Web objects that are requested by one client are stored in a cache, Note and can be retrieved later when another client requests the same object.

For even greater performance, many proxy caches are part of cache hierarchies, in which a cache can enquire neighboring caches for a requested document, to reduce the need to fetch the object directly. Such an organization of multiple cache servers is also referred to as a cache array.

§Reverse proxy: Caches can also be placed directly in front of a particular Web server, to reduce the number of requests that they receive. This model allows the proxy server to respond to the frequently received requests and pass the other requests to the Web server. This form of proxying is called a reverse proxy, wherein the proxy server is used by the Web server to