<?xml version="1.0" encoding="UTF-8"?>
<pin>
  <id type="integer">1309801580</id>
  <code>GBCT</code>
  <expires-at type="dateTime">2020-05-10T18:52:14Z</expires-at>
  <user-id type="integer">231221</user-id>
  <client-identifier>8c89f40c-e1f3-45e1-95bc-a45a047ce77f</client-identifier>
  <trusted type="boolean">false</trusted>
  <auth-token>z6ZM5jeSP19WroEQc2Xy</auth-token>
  <auth_token>z6ZM5jeSP19WroEQc2Xy</auth_token>
</pin>

[XmlRoot("pin")]
public sealed class Pin
{
        [XmlElement("id")]
        public int ID { get; set; }
        [XmlElement("code")]
        public string Code { get; set; }
        [XmlElement("expires-at")]
        public DateTime ExpiresAtUTC { get; set; }
        [XmlElement("auth-token")]
        public string AuthToken { get; set; }
        [XmlElement("client-identifier")]
        public Guid ClientIdentifier { get; set; }
}

string xml = await httpResponse.Content.ReadAsStringAsync().ConfigureAwait(false);
IExtendedXmlSerializer serializer = new ConfigurationContainer().EnableImplicitTypingFromNamespace<Pin>().Create();
using (StringReader stringReader = new StringReader(xml))
{
        returnObj = (TReturn)serializer.Deserialize<TReturn>(stringReader);
}