How to associate custom file extension with VWD Web Form editor

So you have files with .foo extension which you want to behave like they are .aspx in Visual Studio and at runtime? Here is how to make it happen. Let’s say you have file.

1. Open your Web site in VS or Visual Web Developer

2. Tools | Options | Text Editor | File Extensions

3. Type foo in the extension field, choose Web Form Editor from the editor list and click Add and click OK

Now open your Web site web.config file (add one if you don’t yet have it) and check that you have registered .foo with the ASP.NET runtime. If not, add same handler and build provider that is registered for .aspx extension:

                <add extension=”.foo” type=”System.Web.Compilation.PageBuildProvider” appliesTo=”Web” />
            <add path=”*.foo” verb=”*” type=”System.Web.UI.PageHandlerFactory” validate=”True” />

Save the file, open and observe intellisense, coloring and debugging working. Enjoy 🙂

Comments (6)

  1. Hi Mikhail !

    "appliesTo" do not work in August CTP. Do you know the word that replace it ??

    Thanks in advance.

    Eugenio Serrano (ASP.Net MVP)


  2. Just copy-paste whatever line exists in the web.config for aspx extension and change it to refer to your new extension.

  3. Mauricio says:

    i want to know how associate custom file extension in my web host support and where place it? i control my web site by ftp form

  4. web.config is where you add new file associations for the ASP.NET runtime. Basically what I described above after step 3.

  5. David says:

    I have a new extension working for WebForms, but I would like to have Solution Explorer recognize my new extension as a WebForm. How is this done? (What I mean is that I want the context menu for a WebForm on files with my new extension, and I want the code behind file grouped under the html file like aspx files).


  6. In order to get the icon association you need to register file extension in the registry under HKEY_CLASSES_ROOT. Look at how .aspx is registered: it points OpenWithProgid to VisualStudio.aspx.8.0, which key is under the same root and contains point to the icon (as a dll name and # of icon in the dll resources.

    Have a look here: on how to make files appear as cascading icons in the Solution Explorer.