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

• Download URLMapping.zip - 4.2 KB (Sample VS 2005 project)

Introduction

(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.

Solution

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.

STEP 1

• 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

STEP 2

• 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.