how to add sitemap.xml file in mvc

I have added sitemap file in my projects.

below is sitemap controller.

public class SitemapController : Controller
{
// GET: Sitemap
public ActionResult Index()
{
StringBuilder sitemap = new StringBuilder();
sitemap.AppendLine("");
sitemap.AppendLine("");
BuildSitemap(new CmsPages().GetAllPages(), new Languages().GetAllLanguages(isActive: true), new GlobalConfigurations().GetGlobalConfiguration(), null, ref sitemap);
sitemap.AppendLine("");
return Content(sitemap.ToString(), "text/xml");
}
private static void BuildSitemap(List cmsPageList, List sitemapLanguages, GlobalConfiguration globalConfiguration, int? pageParentId, ref StringBuilder sitemap)
{
if (cmsPageList.IsNotNull())
{
List sitemapPages = (from page in cmsPageList
where page.PageParentId == pageParentId
&& page.ShowInSitemap
&& page.IsActive
select page).ToList();
if (sitemapPages.IsNotNull() && sitemapPages.Count() > 0)
{
foreach (CmsPage page in sitemapPages)
{
foreach (Language language in sitemapLanguages)
{
sitemap.AppendLine(" ");
sitemap.AppendLine(" " + globalConfiguration.DomainName.ToUrl() + (page.IsHomePage ? (language.LanguageCode != globalConfiguration.DefaultLanguageCode ? language.LanguageCode + "/" : "") : language.LanguageCode + "/" + page.FullSegment + "/") + "");
foreach (Language languageSubset in sitemapLanguages)
{
sitemap.AppendLine(" + languageSubset.LanguageCode + "\" href=\"" + globalConfiguration.DomainName.ToUrl() + (page.IsHomePage ? (languageSubset.LanguageCode != globalConfiguration.DefaultLanguageCode ? languageSubset.LanguageCode + "/" : "") : languageSubset.LanguageCode + "/" + page.FullSegment + "/") + "\" />");
}
sitemap.AppendLine(" ");
}
BuildSitemap(cmsPageList, sitemapLanguages, globalConfiguration, page.PageId, ref sitemap);
}
}
}
}
}

route.config code for sitemap

routes.MapRoute(
name: "Sitemap",
url: "sitemap.xml",
defaults: new { controller = "Sitemap", action = "Index" }
);

web.config site map url

<handlers>
<add name="SitemapXmlHandler" path="sitemap.xml" verb="GET" type="System.Web.Handlers.TransferRequestHandler" />
handlers>

please where is issue for sitemap.