How to add custom xml tags to sitemap.xml using mvcsitemapprovider?

well, I could not use the mvcsitemapprovider to achieve my goal yet, but I made this temporary solution and I am trying to make nuget package from it or add it as a feature to the mvcsitemapprovider package, here is the code I added to an ContentResult in a controller and I changed my routeConfig to call this method when the url is look like this "/videoSiteMap.xml" :

public ContentResult VideoSiteMap()
    {
        XmlDocument xmlDoc = new XmlDocument();
        using (XmlWriter writer = xmlDoc.CreateNavigator().AppendChild())
        {
            //writer.Formatting = Formatting.Indented;
            writer.WriteStartDocument();
            writer.WriteStartElement("urlset", "http://www.sitemaps.org/schemas/sitemap/0.9");

            // add namespaces
            writer.WriteAttributeString("xmlns", "video", null, "http://www.google.com/schemas/sitemap-video/1.1");
            List<VideoSiteMap> siteMapp = null;
            siteMapp = ServiceHelper.GetGoogleSiteMap();//I invoked a service
            //you can use a fake loop instead: for (int i = 0; i < 10; i++)
            foreach( var content in siteMapp)
            {
                writer.WriteStartElement("url");

                // required
                writer.WriteElementString("loc", "http://example.com/myplayer.aspx");
                writer.WriteStartElement("video", "video", null);

                // start:optional
                writer.WriteElementString("video", "thumbnail_loc", null, "http://www.example.com/thumbs/123.jpg");
                writer.WriteElementString("video", "title", null, "");
                writer.WriteElementString("video", "description", null, "Alkis shows you how to get perfectly done steaks every time");
                writer.WriteElementString("video", "content_loc", null, "http://www.example.com/video123.mp4");

                writer.WriteStartElement("video", "player_loc", null);
                writer.WriteAttributeString("autoplay", "ap=1");
                writer.WriteString("http://www.example.com/videoplayer.mp4?video=123");
                writer.WriteEndElement(); // video:player_loc
                                          // end:optional

                writer.WriteElementString("video", "duration", null, "100");
                writer.WriteElementString("video", "expiration_date", null, "2009-11-05T19:20:30+08:00");
                writer.WriteElementString("video", "rating", null, "4.2");
                writer.WriteElementString("video", "view_count", null, "12345");
                writer.WriteElementString("video", "publication_date", null, "2007-11-05T19:20:30+08:00");
                writer.WriteElementString("video", "family_friendly", null, "yes");
                writer.WriteElementString("video", "category", null, "Cooking");

                writer.WriteStartElement("video", "restriction", null);
                writer.WriteAttributeString("relationship", "allow");
                writer.WriteString("IE GB US CA");
                writer.WriteEndElement();

                writer.WriteStartElement("video", "gallery_loc", null);
                writer.WriteAttributeString("title", "Cooking Videos");
                writer.WriteString("http://cooking.example.com");
                writer.WriteEndElement();

                writer.WriteStartElement("video", "price", null);
                writer.WriteAttributeString("currency", "EUR");
                writer.WriteString("1.99");
                writer.WriteEndElement();

                writer.WriteElementString("video", "requires_subscription", null, "yes");

                writer.WriteStartElement("video", "uploader", null);
                writer.WriteAttributeString("info", "http://www.example.com/users/grillymcgrillerson");
                writer.WriteString("GrillyMcGrillerson");
                writer.WriteEndElement();

                writer.WriteElementString("video", "live", null, "No");

                writer.WriteEndElement(); // video:video
                writer.WriteEndElement(); //url
            }

            writer.WriteEndElement(); //urlset 
            writer.WriteEndDocument();
            writer.Close();
        }

        var stringWriter = new StringWriter();
        var xmlTextWriter = XmlWriter.Create(stringWriter);
        xmlDoc.WriteTo(xmlTextWriter);
        xmlTextWriter.Flush();
        return Content(stringWriter.GetStringBuilder().ToString().replace("utf-16","utf-8"), "text/xml", Encoding.UTF8);

    }

I replaced utf-16 with utf-8 while returning my xml data because I could not find an easier way to change XmlWriter's result (by default it always returns a utf-16 format)

I hope it help the others, I will be glad if someone help me to make it a nuget package or something :D