Switching between ViewEngines with partial views doesn't find the view to display

Question

I have a legacy application that was made with Web-Forms, and trying to use asp.net mvc to render a content inside a partial view. Following @ScottHanselman post of MixingRazorViewsAndWebFormsMasterPagesWithASPNETMVC3 and finally Matt Honeycutt approach http://trycatchfail.com/blog/post/ASPNET-MVC-3-Razor-C-and-VBNET-WebForms-Using-Razor-Views-With-WebForms-Master-Pages

I ended with a view inside my web-form page

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/MyMasterSite.Master" AutoEventWireup="false"
    CodeBehind="InvoiceProfileReport.aspx.cs" Inherits="MyWebFormsNameSpace" %>
<%@ Import namespace="MyMvc.MvcReports.Controllers" %>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="ContentPlaceHolder1">
    <%= this.BlackMagicMVC().Partial("HomepageWidget") %>
</asp:Content>

as you can see I am trying to insert HomepageWidget that is inside of my View folder

Solution Explorer

My controller creates a wrapper around the request, Partial is an extension method

public class BlackMagicMvcHelper
    {
        private static HtmlHelper GetHtmlHelper()
        {
            var controllerContext = new ControllerContext
            {
                HttpContext = new HttpContextWrapper(HttpContext.Current),
                RouteData = new RouteData()
            };

            controllerContext.RouteData.Values["controller"] = "does-not-exist";

            var context = new ViewContext(controllerContext,
                new WebFormView(controllerContext, "does-not-exist", string.Empty),
                new ViewDataDictionary(),
                new TempDataDictionary(),
                TextWriter.Null);

            var helper = new HtmlHelper(context, new ViewPage());

            return helper;
        }

        public MvcHtmlString ActionLink<TController>(Expression<Action<TController>> action, string linkText) where TController : Controller
        {
            var helper = GetHtmlHelper();
            return helper.ActionLink(action, linkText);
        }

        public MvcHtmlString Partial(string partialName)
        {
            var helper = GetHtmlHelper();
            return helper.Partial(partialName);
        }

        public MvcHtmlString RenderAction<TController>(Expression<Action<TController>> action) where TController : Controller
        {
            var helper = GetHtmlHelper();

            var routeValues = ExpressionHelper.GetRouteValuesFromExpression(action);

            return helper.Action((string)routeValues["action"], (string)routeValues["controller"], routeValues);
        }
    }

After loading the page I am getting the error:

The partial view 'HomepageWidget' was not found or no view engine supports the searched locations. The following locations were searched:

~/Views/does-not-exist/HomepageWidget.aspx
~/Views/does-not-exist/HomepageWidget.ascx
~/Views/Shared/HomepageWidget.aspx
~/Views/Shared/HomepageWidget.ascx
~/Views/does-not-exist/HomepageWidget.cshtml
~/Views/does-not-exist/HomepageWidget.vbhtml
~/Views/Shared/HomepageWidget.cshtml
~/Views/Shared/HomepageWidget.vbhtml

Any suggestion of what I am doing wrong?