URL Rewriting in Asp.net using URLRewriter

URL Rewriting in asp.net (c#). (Download Example Project for URL Rewriting in asp.net at the end of this article)

One way to get yourselves rated better in the search engines is to get rid of the basic aspx page and replace it with something much more descriptive i.e.:

If I were selling Nokia phones, I may have a page called http://www.mydomain.com/nokia.aspx – not much good if I am trying to target a specific phone though is it? What about this then?


Much more descriptive and much more likely to get the search engines juices flowing more and hence get you rated higher in the listings.

After searching around for a few solutions, I found this article by Scott GU (Microsoft Guru Extraordinaire) http://weblogs.asp.net/scottgu/archive/2007/02/26/tip-trick-url-rewriting-with-asp-net.aspx which got me excited.

He mentions a few methods, one of which I use on http://www.simonantony.co.uk which is running IIS7 by using the Rewrite module built into IIS – works a treat and has allowed me to convert a static html site into a more dynamic and search engine friendly version.

The other is to use a library from http://urlrewriter.net/ which is the other route I have taken. I’ve successfully implemented this on a project I am currently working upon and thought it would be nice of me to post some fully working example code that you can actually understand – the examples on the urlrewriter website/demos are very poor and not clear at all – no wonder so many people struggle to get it working.

Some blurb from the URLRewriting website will explain it more:

UrlRewriter.NET is an open-source, light-weight, highly configurable URL rewriting component for ASP.NET 1.1 and 2.0. UrlRewriter.NET provides similar IIS Rewrite capabilities that the Apache web server provides with mod_rewrite and .htaccess. You don’t need to install an ISAPI Rewrite filter to use the component. Best of all, UrlRewriter.NET is free and licensed with a very permissive MIT-style licence.

UrlRewriter.NET is a great Search Engine Optimization (SEO) tool. Using UrlRewriter.NET, you can create URL’s containing your target keywords, boosting your rankings.

With UrlRewriter.NET, you can:

* Rewrite URL’s from “user and Search Engine” friendly urls to the actual .aspx pages (also known as URL Masking, IIS Rewrite or ASP Rewrite)
* Redirect from old URL patterns to the new ones, ensuring the Search Engine spiders continue to follow your links (also known as URL Replace)
* Block certain visitors based on the User-Agent – very helpful for blocking crawlers that don’t obey the robots.txt protocol
* Ban users based on IP range (provides the capabilities of mod_rewrite on IIS)
* And much more…

UrlRewriter.NET is a pure .NET component written in C#, and does not require any ISAPI rewrite dll’s to be installed in IIS. You configure rules in a very readable XML format, either in your web.config file or an external rewriter configuration file.

UrlRewriter.NET is in use in many websites large and small such as DotNetKicks, and is embedded in several open source packages, such as the fantastic Yet Another Forum.NET.

Anyway here is how the project is constructed and how to get it working.

  1. Create a new web project – I am using C# but if you really want to you can use VB
  2. Download the urlrewriting library from the official site http://urlrewriter.net
  3. Add a reference to the UrlRewritingNet.UrlRewriter.dll to your project
  4. Open up the web.config file and replace the content with the following code:

<?xml version=”1.0″?>
<section name=”urlrewritingnet” requirePermission=”false”  type=”UrlRewritingNet.Configuration.UrlRewriteSection, UrlRewritingNet.UrlRewriter”  />

xmlns=”http://www.urlrewriting.net/schemas/config/2006/07″ >
<add name=”this-is-a-long-page-name”  virtualUrl=”^~/this-is-a-long-page-name”
ignoreCase=”true” />

<add name=”Product-Search-uk”  virtualUrl=”^~/Product-Search-uk”
ignoreCase=”true” />

<add name=”submit-your-company”  virtualUrl=”^~/submit-your-company”
ignoreCase=”true” />

<add name=”this-is-my-site-blog”  virtualUrl=”^~/this-is-my-site-blog”
ignoreCase=”true” />

<add name=”contact-my-company”  virtualUrl=”^~/contact-my-company”
ignoreCase=”true” />

<add name=”Product-Search-uk-partnumber”  virtualUrl=”^~/product(.*).aspx”
ignoreCase=”true” />

<!–<add name=”Rewrite”  virtualUrl=”^~/(.*)/Detail(.*).aspx”
ignoreCase=”true” />

<add name=”RedirectInApplication”  virtualUrl=”^~/(.*)/Default.aspx”
ignoreCase=”true” />

<add name=”KickBrowserToDomain”  virtualUrl=”^http://(.*)/SampleWeb/kickto/(.*).aspx”
ignoreCase=”true” />–>

<customErrors mode=”Off”>
<add name=”UrlRewriteModule” type=”UrlRewritingNet.Web.UrlRewriteModule, UrlRewritingNet.UrlRewriter” />
<compilation debug=”true” />

    • Create the aspx pages
      1. blog.aspx
      2. contact.aspx
      3. default.aspx (this should already exist)
      4. longpage.aspx
      5. search.aspx
      6. submit_company.aspx
        • In Default.aspx add the following code:

          <div id=”nav”>
          <div id=”navcontainer”>
          <ul id=”navlist”>
          <li><a href=”default.aspx”>Home</a></li>
          <li><a href=”this-is-a-long-page-name”>this-is-a-long-page-name</a></li>
          <li><a href=”Product-Search-uk”>Product Search</a></li>
          <li><a href=”submit-your-company”>Submit your company</a></li>
          <li><a href=”this-is-my-site-blog”>Blog</a></li>
          <li><a href=”contact-my-company”>Contact</a></li>
          <li><a href=”product123.aspx”>Note that this aspx page does not actually exist – click it and see what happens</a></li>


          You will notice that the href links are defined in the web.config file.

            • In search.aspx, add the following html code:

              This is the region page – if you click on <a href=”product12345.aspx”>product12345.aspx</a>, you will be redirected here but the code will show the arguments of the page i.e. 12345 – confused? You will be!


                • Now open up the code behind file for search.aspx and add in the Page_Load event:

                  if(Request.QueryString[“id”] != null)
                  Response.Write(“querystring passed in: ” + Request.QueryString[“id”]);
                  Response.Write(“No query string passed in”);

                    • Run the project. If you click on the search link, you will be taken to the search page but notice the URL in the browser window as it should be reading Product-Search-UK. Same for the other url’s as well except for the last one, if you click on that, a product id will be passed into the page as a querystring that you can use to display specific products on a single page – clever eh!

                      Anyway I hope this has helped you understand how to get a basic implementation of URL Rewriting in your site – i’d love to hear of any more examples you have used, if you want to post them here let me know.


                      Download Example Project for URL Rewriting in asp.net

                      8 thoughts on “URL Rewriting in Asp.net using URLRewriter

                        1. Hi,

                          Sorry but I don’t have any Visual Studio compilers that build to 1.1 anymore – if you find one, feel free to let me know and i’ll add it for you though


                      1. i am gettin this error. Please help me.

                        Object reference not set to an instance of an object.
                        Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

                        Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

                        Source Error:

                        An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

                        Stack Trace:

                        [NullReferenceException: Object reference not set to an instance of an object.]

                        [TypeInitializationException: The type initializer for “Intelligencia.UrlRewriter.RewriterHttpModule” threw an exception.]

                        [TargetInvocationException: Exception has been thrown by the target of an invocation.]
                        System.RuntimeType.CreateInstanceImpl(Boolean publicOnly) +0
                        System.Activator.CreateInstance(Type type, Boolean nonPublic) +66
                        System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes) +655
                        System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes) +200
                        System.Web.Configuration.ModulesEntry.Create() +33
                        System.Web.Configuration.HttpModulesConfiguration.CreateModules() +103
                        System.Web.HttpApplication.InitModules() +45
                        System.Web.HttpApplication.InitInternal(HttpContext context, HttpApplicationState state, MethodInfo[] handlers) +1295
                        System.Web.HttpApplicationFactory.GetNormalApplicationInstance(HttpContext context) +392
                        System.Web.HttpApplicationFactory.GetApplicationInstance(HttpContext context) +256
                        System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr) +414

                        Version Information: Microsoft .NET Framework Version:1.1.4322.573; ASP.NET Version:1.1.4322.573

                        1. This basically means you have created an object but you are trying to use it before initializing it i.e.:

                          Object MyName;

                          MyName.SomeMethod(); // this will throw the exception - do the following to fix

                          MyName = new MyName();

                          MyName.SomeMethod(); //this will work fine


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