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());
            }
        }