Simple Atom feed reader implementation

SyndicationClient.cs

internal class SyndicationClient : ISyndicationClient
{
    private const string XmlnsAtom2005 = "http://www.w3.org/2005/Atom";

    public async Task<FeedDto> RetrieveFeedAsync(Uri uri)
    {
        XDocument doc;
        using (var client = new HttpClient())
        using (var stream = await client.GetStreamAsync(uri).ConfigureAwait(false))
        {
            doc = XDocument.Load(stream);
        }
        var root = doc.Root;
        if (root.Name.NamespaceName == XmlnsAtom2005)
        {
            var titleName = XName.Get("title", XmlnsAtom2005);
            var entryName = XName.Get("entry", XmlnsAtom2005);
            var linkName = XName.Get("link", XmlnsAtom2005);
            var publishedName = XName.Get("published", XmlnsAtom2005);
            var updatedName = XName.Get("updated", XmlnsAtom2005);
            var summaryName = XName.Get("summary", XmlnsAtom2005);

            return new FeedDto(RemoveHtmlTags(root.Element(titleName).Value), root.Elements().Where(x => x.Name == XName.Get("entry", XmlnsAtom2005))
                .Select(x => {
                    var date = DateTimeOffset.Parse(x.Element(publishedName).Value, CultureInfo.InvariantCulture);
                    if (date <= new DateTime(1601, 1, 2)) date = DateTimeOffset.Parse(x.Element(updatedName).Value, CultureInfo.InvariantCulture);
                    return new FeedItemDto(new Uri(x.Element(linkName).Attribute("href").Value),
                        date,
                        RemoveHtmlTags(x.Element(titleName).Value),
                        RemoveHtmlTags(x.Element(summaryName).Value));
                }).ToArray());
        }

        throw new NotSupportedException(root.Name.NamespaceName);
    }

    private static string RemoveHtmlTags(string message)
    {
        if (string.IsNullOrEmpty(message)) { return message; }
        message = WebUtility.HtmlDecode(message);
        return Regex.Replace(Regex.Replace(message, "\\&.{0,4}\\;", ""), "<.*?>", "");
    }
}

public sealed class FeedDto
{
    public FeedDto(string title, IReadOnlyList<FeedItemDto> items)
    {
        Title = title;
        Items = items;
    }

    public string Title { get; }

    public IReadOnlyList<FeedItemDto> Items { get; }
}

public sealed class FeedItemDto
{
    public FeedItemDto(Uri uri, DateTimeOffset date, string name, string description)
    {
        Uri = uri;
        Date = date;
        Name = name;
        Description = description;
    }

    public Uri Uri { get; }

    public DateTimeOffset Date { get; }

    public string Name { get; }

    public string Description { get; }
}