How to create an Xml Sitemap in Umbraco V9

ISiteMapXmlService.cs

public interface ISiteMapXmlService
{
    public string GenerateXml();
}

PublishedContentExtensions.cs

using Umbraco.Cms.Core.Models.PublishedContent;
using Umbraco.Extensions;

public static class PublishedContentExtensions
{
    public static bool HasTemplate(this IPublishedContent content) => content.TemplateId > 0;

    public static bool IsInSiteMap(this IPublishedContent content) => !content.Value<bool>("hideFromXmlSitemap", defaultValue: false) && content.HasTemplate();

}

SiteMapXmlService.cs

using System.Linq;
using System.Xml.Linq;
using Umbraco.Cms.Core.Models.PublishedContent;
using Umbraco.Cms.Core.Web;
using Umbraco.Extensions;

/// <summary>
/// Generates an XML sitemap
/// </summary>
public class SiteMapXmlService : ISiteMapXmlService
{
    private readonly IUmbracoContextFactory _umbracoContextFactory;
    private static readonly XNamespace Xmlns = "http://www.sitemaps.org/schemas/sitemap/0.9";

    public SiteMapXmlService(IUmbracoContextFactory umbracoContextFactory)
    {
        _umbracoContextFactory = umbracoContextFactory;
    }

    public string GenerateXml()
    {
        using var context = _umbracoContextFactory.EnsureUmbracoContext();
        var rootNode = context.UmbracoContext.Content.GetByXPath("//home").First();
        var nodes = rootNode
            .DescendantsOrSelf()
            .Where(x => x.HasTemplate())
            .Where(x => x.IsVisible())
            .Where(x => x.Value<bool>("hideFromXmlSitemap") == false);

        XElement root = new XElement(Xmlns + "urlset");

        foreach (var node in nodes)
        {
            var urlElement = new XElement(Xmlns + "url", 
                new XElement(Xmlns + "loc", node.Url(mode: UrlMode.Absolute)), 
                new XElement(Xmlns + "lastmod", node.UpdateDate.ToString("yyyy-MM-dd")));

            var changeFreqency = node.Value<string>("searchEngineChangeFrequency");

            if (string.IsNullOrWhiteSpace(changeFreqency) == false)
            {
                urlElement.Add(new XElement(Xmlns + "changefreq", changeFreqency.ToLower()));
            }

            var priority = node.Value<decimal>("searchEngineRelativePriority");

            if (priority > 0)
            {
                urlElement.Add(new XElement(Xmlns + "priority", priority));
            }

            root.Add(urlElement);
        }

        XDocument document = new XDocument(root);

        var sitemapXml = document.ToString();

        return sitemapXml;
    }
}

XmlSiteMapSurfaceController.cs

using System.Text;
using Microsoft.AspNetCore.Mvc;
using Umbraco.Cms.Core.Cache;
using Umbraco.Cms.Core.Logging;
using Umbraco.Cms.Core.Routing;
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Core.Web;
using Umbraco.Cms.Infrastructure.Persistence;
using Umbraco.Cms.Web.Website.Controllers;

public class XmlSiteMapSurfaceController : SurfaceController
{
    private readonly ISiteMapXmlService _xmlSiteMapXmlService;
    [Route("sitemap.xml")]
    [ResponseCache(Duration = 900)]
    public ContentResult Index()
    {
        return Content(_xmlSiteMapXmlService.GenerateXml(), "text/xml", Encoding.UTF8);
    }

    public XmlSiteMapSurfaceController(IUmbracoContextAccessor umbracoContextAccessor, IUmbracoDatabaseFactory databaseFactory, ServiceContext services, AppCaches appCaches, IProfilingLogger profilingLogger, IPublishedUrlProvider publishedUrlProvider, ISiteMapXmlService xmlSiteMapXmlService) 
        : base(umbracoContextAccessor, databaseFactory, services, appCaches, profilingLogger, publishedUrlProvider)
    {
        _xmlSiteMapXmlService = xmlSiteMapXmlService;
    }
}