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Posted 8 Apr 2007


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URL Mapping / URL Rewriting / Search Engine Friendly URLs / Virtual URLs (ASP.NET)

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20 Apr 2007CPOL1 min read
URL Mapping / URL Rewriting / Search Engine Friendly URLs / Virtual URLs with postbacks in ASP.NET C# (Without hardcoding in Web.Config)


(ASP.NET, C#, Visual Studio 2005)

Hi folks; Recently, I built a custom Content Management Software for a website. The client wanted the page contents to be served from database by a page ShowContents.aspx?ContentID=XX.
The main requirements were as follows:

  • Search engine friendly URLs (i.e. They would like "/finance/loan.aspx" instead of "ShowContents.aspx?ID=23").
  • Hardcoding URLs in Web.Config's URLMapping section was not an option, as there were no physical pages to map to.
  • Postback should still work on all these virtual URLs.
  • References to the images, css files, and themes should stay intact.


After a day's research, I came up with this really simple solution. I thought I should sum up the knowledge collected from various sources and make it public for everyone to benefit.
You can integrate following steps in to your existing ASP.NET project, or you can create a new one.


  • Create "ShowContents.aspx", that serves content based on the ContentID passed in the QueryString.
  • To enable postbacks to the raw URL in the Page_Load() event of ShowContents.aspx, insert following line Context.RewritePath(Path.GetFileName(Request.RawUrl)); // needs System.IO


  • Capture the URL requested by the user in the Application_BeginRequest() event of Global.asax.
  • Find the ID of the content from database that is relevant to this URL
  • ReWritePath to ShowContents.aspx?ContentID=XX. The user will see requested URL in the address bar with the desired content.
  • Any files that physically exist on the server will still get served as usual.

Using the code

// STEP 1 (ShowContents.aspx)
// This page displays contents from a database for a ContentID. This file
// must contain the following line in it's Page_Load() event.
Context.RewritePath(Path.GetFileName(Request.RawUrl)); //needs System.IO

// STEP 2 (Global.asax)
// Following code goes in your Global.asax file, in the root directory of
// the project. This file captures the incoming requests' URL, gets the 
// Content ID of the content related to the URL and redirects the user to
// ShowContents.aspx?ContentID=XX. While the user still sees the requested 
// URL in the address bar.

    <%@ Import Namespace="System.IO" %>
    protected void Application_BeginRequest(object sender, EventArgs e)
        // If the requested file exists
        if (File.Exists(Request.PhysicalPath))
                // Do nothing here, just serve the file
        // If the file does not exist then
        else if (!File.Exists(Request.PhysicalPath))
            // Get the URL requested by the user
            string sRequestedURL = Request.Path.Replace(".aspx", "");
            // You can retrieve the ID of the content from database that is 
            // relevant to this requested URL (as per your business logic)
            int nId = 0;        
            ////// nId = GetContentIDByPath(sRequestedURL); \\\\\

           // The ShowContents.aspx page should show contents relevant to 
           // the ID that is passed here
            string sTargetURL = "~/ShowContents.aspx?ContentID=" + nId.ToString();

            // Owing to RewritePath, the user will see requested URL in the
        // address bar
            // The second argument should be false, to keep your references
        // to images, css files
            Context.RewritePath(sTargetURL, false);
//  That's all! :-) 

Hope this helps you save time on researching various sources. You might like to download the zip file containing a sample VS 2005 project.

Feedback is welcome and appreciated.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Web Developer
United States United States
Manu Agrawal is a .NET developer living in the USA.
He has good professional web development experience (mainly in ASP.NET, C#). He enjoys developing high performance and secure websites.
He holds a master's degree in E-Commerce and Management from London, UK.

Comments and Discussions

GeneralProblems with postback and UpdatePanel Pin
marco vervoort12-Apr-07 2:07
Membermarco vervoort12-Apr-07 2:07 
AnswerRe: Problems with postback and UpdatePanel Pin
mplusplus2-May-07 4:20
Membermplusplus2-May-07 4:20 
Generalthanks for the postback thingy Pin
robert_fairbrother9-Apr-07 22:37
Memberrobert_fairbrother9-Apr-07 22:37 
GeneralCool Pin
Ben Daniel9-Apr-07 20:50
MemberBen Daniel9-Apr-07 20:50 
GeneralRe: Cool Pin
mplusplus14-Apr-07 12:06
Membermplusplus14-Apr-07 12:06 
GeneralRe: Cool Pin
stixoffire7-Oct-07 20:46
Memberstixoffire7-Oct-07 20:46 Pin
matt from ne8-Apr-07 17:56
Membermatt from ne8-Apr-07 17:56 
QuestionA problem with extensions Pin
p daddy8-Apr-07 10:25
Memberp daddy8-Apr-07 10:25 
One of your requirements that you mentioned ("The virtual URLs requsted by the user may or may not have file extensions.") is something I've researched in the past too.

The problem, as I understand it, is that when your application is running under VS.NET, everything is tickety-boo. You request a URL like /finance/loan, the development web server passes this to ASP.NET, at which point you catch it in global.asax, you see the file doesnt exist and serve something else, perhaps from a database, instead.

However, when you run the same code under IIS, aspnet_isapi.dll is only invoked for file extensions that are mapped in the IIS configuration. Basically, your code is never called because "/finance/loan" is not recognised by IIS as a request that needs ASP.NET.

I've just tested your code and my suspicions were right:

In the VS.NET development web server:
http://localhost:1968/URLMapping/finance/loan works perfectly;

Under IIS:
http://localhost/urlmapping/finance/loan gives a standard 404.

We can make your code work in IIS:

but only by adding .aspx to the end, as this invokes ASP.NET before IIS realises the file doesnt exist.

Annoying, but it seems ISAPI is the only way to catch these kind of requests without big configuration changes. Anybody got this working well with "free" code?



AnswerRe: A problem with extensions Pin
mplusplus8-Apr-07 10:35
Membermplusplus8-Apr-07 10:35 
GeneralRe: A problem with extensions Pin
Furty8-Apr-07 15:09
MemberFurty8-Apr-07 15:09 
AnswerWell actually you can sorta capture requests for extensionless files Pin
volkan.ozcelik9-Apr-07 8:19
Membervolkan.ozcelik9-Apr-07 8:19 
GeneralRe: Well actually you can sorta capture requests for extensionless files Pin
danielkennedy9-Apr-07 20:58
Memberdanielkennedy9-Apr-07 20:58 
GeneralRe: Well actually you can sorta capture requests for extensionless files Pin
volkan.ozcelik10-Apr-07 21:45
Membervolkan.ozcelik10-Apr-07 21:45 
GeneralRe: Well actually you can sorta capture requests for extensionless files Pin
John9703018-Apr-07 9:11
MemberJohn9703018-Apr-07 9:11 
AnswerRe: A problem with extensions Pin
stixoffire7-Oct-07 20:44
Memberstixoffire7-Oct-07 20:44 

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