BuildAlternateLinkElement.cs

/////// FROM ///////
protected static XNamespace Xhtml { get; } = (XNamespace) "http://www.w3.org/1999/XMLSchema-instance";

protected virtual XElement BuildAlternateLinkElement(string href, string hreflang, string rel = "alternate") => new XElement(SitemapGenerator.Xhtml + "link", new object[3]
{
  (object) new XAttribute((XName) nameof (rel), (object) rel),
  (object) new XAttribute((XName) nameof (hreflang), (object) hreflang),
  (object) new XAttribute((XName) nameof (href), (object) href)
});

/////// TO ///////
protected static XNamespace Xhtml { get; } = (XNamespace) "http://www.w3.org/2001/XMLSchema-instance";

protected virtual XElement BuildAlternateLinkElement(string href, string hreflang, string rel = "alternate") => new XElement(YourClassName.Xhtml + "link", new object[3]
{
  (object) new XAttribute((XName) nameof (rel), (object) rel),
  (object) new XAttribute((XName) nameof (hreflang), (object) hreflang),
  (object) new XAttribute((XName) nameof (href), (object) href)
});