public void as_xml_textreader()
    {
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.AsXml<object>(null));

      var subject = Guid.Empty;
      using (var reader = new StringReader(subject.ToXml()))
      {
        Assert.True(reader.AsXml<Guid>() == subject);
        reader.ReadLine();
      }
      using (var reader = new StringReader(subject.ToXml()))
      {
        Assert.Equal(subject, reader.AsXml<Guid>(true));
        Assert.Throws<ObjectDisposedException>(() => reader.ReadLine());
      }
    }