How to add extra namespaces to Razor pages instead of @using declaration?

Question

Update: please take a look at my updated answer that applies to MVC 3 RC: Razor HtmlHelper Extensions (or other namespaces for views) Not Found

This has changed between MVC 3 Preview 1 and MVC 3 Beta (released just today). In Preview 1 Razor used the WebForms namespaces config section. However in the Beta there is a new config section that is seperate from the WebForms one. You will need to add the follwing to your web.config file (or just start with a brand new project from the template):

<configSections>
  <sectionGroup name="system.web.webPages.razor" type="System.Web.WebPages.Razor.Configuration.RazorWebSectionGroup, System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
    <section name="host" type="System.Web.WebPages.Razor.Configuration.HostSection, System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
    <section name="pages" type="System.Web.WebPages.Razor.Configuration.RazorPagesSection, System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
  </sectionGroup>
</configSections>

<system.web.webPages.razor>
  <pages pageBaseType="System.Web.Mvc.WebViewPage">
    <namespaces>
      <add namespace="MyCustomHelpers" />
    </namespaces>
  </pages>
</system.web.webPages.razor>

Note that you might need to close and reopen the file for the changes to be picked up by the editor.

Note that there are other changes to what is required in web.config to get Razor to work in MVC3 Beta so you would be best off to take a look at the ~\View\Web.config file that ships in the Beta project templates.

If you put your namespace declaration in the Web.config in the root "Views" folder and/or the current area's "Views" folder (depending on where your view is) - it should work as expected.

I found this http://weblogs.asp.net/mikaelsoderstrom/archive/2010/07/30/add-namespaces-with-razor.aspx which explains how to add a custom namespace to all your razor pages.

Basically you can make this

using Microsoft.WebPages.Compilation;
public class PreApplicationStart
{
   public static void InitializeApplication()
   {
       CodeGeneratorSettings.AddGlobalImport("Custom.Namespace");
   }
}

and put the following code in your AssemblyInfo.cs

[assembly: PreApplicationStartMethod(typeof(PreApplicationStart), "InitializeApplication")]

the method InitializeApplication will be executed before Application_Start in global.asax

For what it's worth, another technique is to simply put your helper extension class in a System namespace that is already included by the view engine by default. For example:

namespace System.Web.Mvc
{
    public static class HtmlHelper_MyExtensions
    {
        ...
    }
}

This way, as long as the library containing the class is referenced, everything will see it. Since you are extending a System.Web.Mvc class, it seems reasonably acceptable to put the extension methods in the same namespace.