ASP.NET WebForms Routing

22 Jun

This post is more of a “technical completion” post for using Routing in WebForms, which covers some of the issues I have come across. If you require a quick start on Routing, or technical MVC stuff, please read this post first.

I was happy to learn that it’s quite easy to use MS’ built-in Url Routing solution for ASP.NET WebForms. This is quite easy to accomplish in IIS 7, and requires some tweaking in IIS 6. Read this on how to configure your web.config file to support routing according to your IIS configuration. You may want to check that Url Routing is installed.

One pit fall that I’ve encountered was when I needed to deploy a routing solution on a certain server. There seemed to be a slight configuration difference from my development machine, and routing did not work. What I eventually did was to perform a minor tweak in the configuration file, and added a runAllManagedModulesForAllRequests as described here. Note that there are those who consider this configuration tweak “inappropriate” as far as performance, resources and error prone, but their suggested solutions didn’t seem to solve my issue. I decided to perform a simple check, what ASP.NET MVC’s template is configured like – and runAllManagedModulesForAllRequests=true is exactly that. I reckon that if the guys at MS provide this configuration in ASP.NET MVC, it’s good enough for WebForms too.

Enough with the configuration, where are those pitfalls?

As with ASP.NET MVC, the routes are set in the Global.asax file. Here are some routes that will be used in this post:

get.aspx is the sample page in this post. It contains a single PageMethod and will be our test case:

Unlike Web Services (asmx) WebMethods, there is an issue with Url Routing when it comes to PageMethods. It seems like the client is unable to provide the correct url for the page, and the server seems to fail in figuring out which page and method should be invoked. The error received in the client is “405 Method Not Allowed“, and the response contains a somewhat confusing “The HTTP verb POST used to access path ‘…’ is not allowed.” message, which basically means that the Url isn’t resolved correctly and therefore does not reach the correct PageMethod.

Indeed, the Url the client sends by default to our get.aspx page is: “http://localhost:54885/WebSite2/get/1/Get”.

  • The first “get” is the route which routes to get.aspx;
  • The “1” is a simple {id}.
  • The second “Get” is the PageMethod.

Because we received the 405 error message, I used the Route Debugger, and as expected, the Route Debugger showed a “No Match” on that url. Initially I thought that it would be easy to write a RouteHandler and provide a generic solution for PageMethod urls, but after I started coding I noticed that it’s not as easy as it may seem. Possible, but not as easy as the workaround. In order to workaround, all you have to do is to set the path in the client JavaScript to the correct page and you’re done. This is done like so:

Note: You can read here how to call your PageMethods using jQuery.

HttpHandlers – ashx files

It seems like ASP.NET 4 has no support for routing to ashx handler files. When you attempt to route to an ashx you’ll get the following exception:

Type ‘MyHandler’ does not inherit from ‘System.Web.UI.Page’.

Fortunately, this is quite easy to get by, because coding a Route handler which will take care of ashx files is trivial enough. Note, that the solution suggested here is based on a Web site and not a Web application, so the route handler code resides in App_Code.

So, there are three steps to this:

  1. Refactor your ashx code to an App_Code class which inherits from IHttpHandler.
  2. Write a simple Route handler which will create that handler when requested to.
  3. Add the new route handler to the routes defined in Global.asax.

Step 1: Refactor the handler – basically, this is your starting point for your actual “business” implementation (although I encourage calling a Business Layer from here):

Step 2: Create a simple Route handler to return the IHttpHandler:

Step 3: Register the new route in Global.asax:

That’s all there is to it. Now you can use a route for targeting your handler, for example:


UPDATE: For routing Web Services (asmx), click here.

Route Data

One last issue is in cases that you perform url rewriting or other processing, and you suddenly notice that your Route Data is gone. This is quite frustrating as you can plainly see that url in the browser’s address bar. Fortunately, the solution is quite simple and also uses a Route Handler. All we have to do, is copy the Route Data in a custom Route handler to HttpContext.Current.Items collection, and we have them for the entire http request. Two steps here:

Step 1: Write a simple custom Route handler which copies the route data:

Step 2: Configure Global.asax accordingly:

To sum up – it’s quite cool to be able to use Routing in WebForms. I just finished a small project where I used Routing and the result is quite awesome. It wasn’t just looking better, but it also allowed me to “white label” the website dynamically. For example, I could do the following: http://server/productA/login and http://server/productB/login, and it really felt like two different websites.


Posted by on 22/06/2011 in Software Development


Tags: , ,

4 responses to “ASP.NET WebForms Routing

  1. Hva Faen

    05/08/2011 at 15:49


    Thanks to you & your clear explanation i can now use ‘clean urls’ with my images


  2. Dan

    18/10/2013 at 03:52

    Wow. Thank you SO MUCH for this explanation. I never would have figured this out on my own.

  3. Tonet

    15/05/2015 at 12:51

    ¡Muchas gracias me sirvió de mucho!, muy bien explicado


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