Logo
PREGNANCY
Windows XP
Windows Vista
Windows 7
Windows Azure
Windows Server
Windows Phone
 
 
Windows XP

Microsoft ASP.NET 4 : HTTP Handlers - The Built-in Handlers

7/8/2011 6:09:18 PM
One of the best examples of custom handling is the Trace handler built into ASP.NET. You turn tracing on in the web.config file by inserting the trace element, <trace enabled=true />. This instructs the ASP.NET runtime to store summaries of the requests going through the site so that they can be viewed for diagnostic purposes.

ASP.NET caches the tracing output in memory. To view the trace results, you surf to the virtual directory managing the site and ask for a specific resource: Trace.axd. Take a look at this Example and you'll see the first entry among all the standard HTTP handlers is for a resource named Trace.axd. The tracing functionality behind ASP.NET falls outside of normal UI processing, so it makes sense that tracing is handled by a custom handler.

When you surf to the Trace.axd resource, the handler renders HTML that looks like the output shown in Figure 1. The processing for this handler is very specific—the handler's job is to render the results of the last few requests.

Figure 1. The output of the Trace.axd handler.


As shown in Figure 2, clicking the View Details link resubmits the request with a parameter id=3 in the query string. This causes the handler to render the details of the third request.

Figure 2. The output of the Trace.axd handler focused on a specific request summary.


Figure 3 shows the Microsoft Internet Information Services (IIS) file mapping for files with the .axd extension. Although you won't really see this aspect until deployment time, it's interesting to observe because it shows how ASP.NET is very versatile in the kinds of requests it can handle. IIS handles Trace.axd requests the same way as any other ASP.NET request. That means IIS will pass requests for resources with an extension of .axd on to ASP.NET. Once inside the ASP.NET pipeline, the web.config file tells ASP.NET to handle the request with the Trace handler.

Figure 3. IIS has a handler mapping for Trace.axd.


If you look through the default web.config file a bit more, you'll see some other critical ASP.NET handlers. As you might expect, source code is banned explicitly from normal clients by default. Notice that files such as *.cs, *.config, and *.vb are handled by the Forbidden handler. If you try to look at source code in a Web browser, ASP.NET returns the page shown in Figure 4 by default.

Figure 4. What happens when you try to view forbidden content.


Remember that ASP.NET's configuration is very malleable and that you can choose to let clients see your source code by one of two means. You can remove the source code extension to ASP.NET mappings in IIS. Alternatively, you can write your own source code viewer handlers and declare them in your application's web.config file.

These handlers plug into the pipeline by implementing IHttpHandler. The next section describes this key interface.
Other -----------------
- Microsoft ASP.NET 4 : ASP.NET Request Handlers
- Microsoft ASP.NET 4 : HttpModules (part 2) - Seeing Active Modules & Storing State in Modules
- Microsoft ASP.NET 4 : HttpModules (part 1) - Existing Modules & Implementing a Module
- Microsoft ASP.NET 4 : The HttpApplication Class and HTTP Modules - Overriding HttpApplication
- Microsoft ASP.NET 4 : Diagnostics and Debugging - Error Pages
- Microsoft ASP.NET 4 : Diagnostics and Debugging - Debugging with Visual Studio
- Microsoft ASP.NET 4 : Diagnostics and Debugging - Application Tracing
- Microsoft ASP.NET 4 : Diagnostics and Debugging - Page Tracing
- Microsoft ASP.NET 4 : Caching and State Management - The Wizard Control: An Alternative to Session State
- Microsoft ASP.NET 4 : Caching and State Management - Tracking Session State
- Microsoft ASP.NET 4 : Caching and State Management - Configuring Session State
- Microsoft ASP.NET 4 : Caching and State Management - Session State and More Complex Data
- Microsoft ASP.NET 4 : Caching and State Management - Introduction to Session State
- Installing and Configuring a Modem : Modifying the Modem’s Advanced Properties
- Installing and Configuring a Modem : Modifying the Modem’s General Properties
- Installing and Configuring a Modem : Working with Different Dialing Locations
- Installing and Configuring a Modem : Installing a Modem & Testing the Modem
- Getting Started with Modem Communications : Modem-to-Modem Communications
- Tuning Windows XP’s Performance : More Optimization Tricks
- Tuning Windows XP’s Performance : Optimizing Virtual Memory
 
 
Most view of day
- Working with the User State Migration Tool (part 5) - Getting Extra Mileage Out of the USMT
- Games and Windows 7 : Games for Windows - LIVE (part 1) - Using the Games for Windows - LIVE Marketplace
- Microsoft Exchange Server 2010 : Working with SMTP Connectors, Sites, and Links (part 4) - Viewing and Managing Send Connectors
- Exchange Server 2007 : Deploying a Cluster Continuous Replication Mailbox Cluster (part 2)
- Windows Server 2003 on HP ProLiant Servers : Build Guides
- Microsoft Visio 2010 : Creating and Using Shape Data Fields (part 1) - Adding Simple Data Fields
- Exploring the Vista Task Scheduler
- Zero Touch Installations : Creating and Capturing a Reference Image (part 1)
- SharePoint 2010 : Packaging and Deployment Model - Features (part 1) - Feature Designer
- Automating Windows 7 Installation : Using Windows System Image Manager (part 2) - Exploring the Components of an Answer File
Top 10
- Microsoft Sharepoint 2013 : Understanding app patterns (part 5) - Building MVC apps - Introducing MVC4
- Microsoft Sharepoint 2013 : Understanding app patterns (part 4) - Building MVC apps - Understanding web form challenges
- Microsoft Sharepoint 2013 : Understanding app patterns (part 3) - Building MVVM apps - Utilizing promises
- Microsoft Sharepoint 2013 : Understanding app patterns (part 3) - Building MVVM apps - Utilizing promises
- Microsoft Sharepoint 2013 : Understanding app patterns (part 2) - Building MVVM apps - Introducing knockout
- Microsoft Sharepoint 2013 : Understanding app patterns (part 1) - Building MVVM apps - Understanding JavaScript challenges
- Microsoft Access 2010 : Report Properties and Why to Use Them, Basing Reports on Stored Queries or Embedded SQL Statements
- Microsoft Access 2010 : Working with Sorting and Grouping (part 2) - Sorting and Grouping Settings
- Microsoft Access 2010 : Working with Sorting and Grouping (part 1) - Add Sorting and Grouping to a Report
- Microsoft Access 2010 : Building Reports Based on More Than One Table (part 3) - Working with Subreports
 
Windows XP
Windows Vista
Windows 7
Windows Azure
Windows Server
Windows Phone
2015 Camaro