How do I use an extension method in an ASP.NET MVC View?

In View:

<%@ Import Namespace="MyProject.Extensions" %>

Or in web.config (for all Views):

<pages>
  <namespaces>
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    <add namespace="System.Web.Routing" />
    <add namespace="System.Linq" />
    <add namespace="System.Collections.Generic" />

    <add namespace="MyProject.Extensions" />
  </namespaces>
</pages>