Get HTML String from PageData in Episerver

ChildActionHandler.cs

using System;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
using System.Web.UI;

/// <summary>
/// Shamelessly "inspired" by classes in System.Web.Mvc assembly
/// It appears that only a System.Web.UI.Page can be executed
/// as a child request. If you try to execute an MvcHandler
/// directly an exception (with no detail) is thrown
/// </summary>
internal class ChildActionHandler : Page, IHttpAsyncHandler
{
    internal class ChildActionMvcHandler : MvcHandler
    {
        public ChildActionMvcHandler(RequestContext context)
            : base(context)
        {
        }

        protected override void AddVersionHeader(HttpContextBase httpContext)
        {
        }
    }

    private readonly ChildActionMvcHandler mvcHandler;

    public ChildActionHandler(RequestContext context)
    {
        this.mvcHandler = new ChildActionMvcHandler(context);
    }

    public override void ProcessRequest(HttpContext context)
    {
        ((IHttpHandler)this.mvcHandler).ProcessRequest(context);
    }

    public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
    {
        return ((IHttpAsyncHandler)this.mvcHandler).BeginProcessRequest(context, cb, extraData);
    }

    public void EndProcessRequest(IAsyncResult result)
    {
        ((IHttpAsyncHandler)this.mvcHandler).EndProcessRequest(result);
    }
}

MvcPageDataRenderer.cs

 using System.Globalization;
 using System.IO;
 using System.Web.Routing;
 using EPiServer.Core;
 using EPiServer.Web;
 using EPiServer.Web.Routing;

 public class MvcPageDataRenderer 
 {
     private readonly TemplateResolver templateResolver;

     public MvcPageDataRenderer(TemplateResolver templateResolver)
     {
         this.templateResolver = templateResolver;
     }

     public string ExecuteChildRequest(RequestContext existingRequestContext, PageData pageToRender, string preferredLanguageToRender)
     {
         var templateModel = this.templateResolver.ResolveMvcTemplate(existingRequestContext.HttpContext, pageToRender);

         existingRequestContext.SetController(templateModel.TemplateType.Name.Replace("Controller", string.Empty));
         existingRequestContext.SetControllerType(templateModel.TemplateType);
         existingRequestContext.SetContentLink(pageToRender.ContentLink);
         existingRequestContext.SetRoutedData(pageToRender);
         existingRequestContext.SetContextMode(ContextMode.Default);

         existingRequestContext.RouteData.Values["action"] = "Index";
         existingRequestContext.RouteData.DataTokens["namespaces"] = new[] { templateModel.TemplateType.Namespace };

         if (!string.IsNullOrWhiteSpace(preferredLanguageToRender))
         {
             existingRequestContext.SetLanguage(preferredLanguageToRender);
             EPiServer.BaseLibrary.Context.Current["EPiServer:ContentLanguage"] = new CultureInfo(preferredLanguageToRender);
         }

         var handler = new ChildActionHandler(existingRequestContext);

         using (var stringWriter = new StringWriter(CultureInfo.CurrentCulture))
         {
             existingRequestContext.HttpContext.Server.Execute(handler, stringWriter, true);
             return stringWriter.ToString();
         }
     }
 }