Analisar XML de sabão em objeto em C #

Eu tenho o seguinte XML SOAP

string soap = "<soapenv:Envelope xmlns:soapenv='http://schemas.xmlsoap.org/soap/envelope/' xmlns:ns='http://schemas.abudhabi.ae/sso/2010/11'>" +
   "<soapenv:Header/>" +
   "<soapenv:Body>" +
      "<ns:GetUserProfileResponse>" +
         "<!--Optional:-->" +
         "<ns:userid>?</ns:userid>" +
         "<!--Optional:-->" +
         "<ns:firstNameAr>?</ns:firstNameAr>" +
         "<!--Optional:-->" +
         "<ns:firstNameEn>?</ns:firstNameEn>" +
         "<!--Optional:-->" +
         "<ns:middleNameAr>?</ns:middleNameAr>" +
         "<!--Optional:-->" +
         "<ns:middleNameEn>?</ns:middleNameEn>" +
         "<!--Optional:-->" +
         "<ns:thirdNameAr>?</ns:thirdNameAr>" +
         "<!--Optional:-->" +
         "<ns:thirdNameEn>?</ns:thirdNameEn>" +
         "<!--Optional:-->" +
         "<ns:fourthNameAr>?</ns:fourthNameAr>" +
         "<!--Optional:-->" +
         "<ns:fourthNameEn>?</ns:fourthNameEn>" +
         "<!--Optional:-->" +
         "<ns:familyNameAr>?</ns:familyNameAr>" +
         "<!--Optional:-->" +
         "<ns:familyNameEn>?</ns:familyNameEn>" +
         "<!--Optional:-->" +
         "<ns:authLevel>?</ns:authLevel>" +
         "<!--Optional:-->" +
         "<ns:dateOfBirth>?</ns:dateOfBirth>" +
         "<!--Optional:-->" +
         "<ns:gender>?</ns:gender>" +
         "<!--Optional:-->" +
         "<ns:nationalityCode>?</ns:nationalityCode>" +
         "<!--Optional:-->" +
         "<ns:idn>?</ns:idn>" +
         "<!--Optional:-->" +
         "<ns:modifyTimestamp>?</ns:modifyTimestamp>" +
         "<!--Optional:-->" +
         "<ns:prefComChannel>?</ns:prefComChannel>" +
         "<!--Optional:-->" +
         "<ns:secretQuestionAnswer>?</ns:secretQuestionAnswer>" +
         "<!--Optional:-->" +
         "<ns:secretQuestionId>?</ns:secretQuestionId>" +
         "<!--Optional:-->" +
         "<ns:address>" +
            "<!--Optional:-->" +
            "<ns:additionalAddressInfo>?</ns:additionalAddressInfo>" +
            "<!--Optional:-->" +
            "<ns:city>?</ns:city>" +
            "<!--Optional:-->" +
            "<ns:fax>?</ns:fax>" +
            "<!--Optional:-->" +
            "<ns:residenceCountry>?</ns:residenceCountry>" +
            "<!--Optional:-->" +
            "<ns:poBox>?</ns:poBox>" +
            "<!--Optional:-->" +
            "<ns:stateOrEmirate>?</ns:stateOrEmirate>" +
            "<!--Optional:-->" +
            "<ns:streetNameAndNumber>?</ns:streetNameAndNumber>" +
            "<!--Optional:-->" +
            "<ns:zipCode>?</ns:zipCode>" +
         "</ns:address>" +
         "<!--Optional:-->" +
         "<ns:contact>" +
            "<!--Optional:-->" +
            "<ns:email>?</ns:email>" +
            "<!--Optional:-->" +
            "<ns:mobilePhoneNumber>?</ns:mobilePhoneNumber>" +
            "<!--Optional:-->" +
            "<ns:website>?</ns:website>" +
            "<!--Optional:-->" +
            "<ns:workPhone>?</ns:workPhone>" +
         "</ns:contact>" +
      "</ns:GetUserProfileResponse>" +
   "</soapenv:Body>" +
"</soapenv:Envelope>";

Queria analisar ou converter na seguinte classe

public class UserProfile
        {
            public string FirstNameAR { get; set; }

            public string FirstNameEN { get; set; }

            public string MiddleNameAR { get; set; }

            public string MiddleNameEN { get; set; }

            public string ThirdNameAR { get; set; }
            public string ThirdNameEN { get; set; }


            public string FourthNameAR { get; set; }

            public string FourthNameEN { get; set; }

            public string FamilyNameAR { get; set; }

            public string FamilyNameEN { get; set; }

            public Boolean AuthLevelSpecified { get; set; }

            public DateTime DateOfBirth { get; set; }
            public bool DateOfBirthSpecified { get; set; }


            public Boolean GenderTypeSpecified { get; set; }

            public string NationalityCode { get; set; }

            public string IDN { get; set; }

            public Boolean ModifyTimeStampSpecified { get; set; }
            public DateTime ModifyTimeStamp { get; set; }

            //  public PrefComChannelType PrefComChannelType { get; set; }
            public Boolean PrefComChannelTypeSpecified { get; set; }

            public string SecretQuestion { get; set; }

            public int SecretQuestionId { get; set; }

            public Boolean SecretQuestionSpecified { get; set; }
           }

e meu código é:

var Value = XDocument.Parse(soap);

XNamespace ns = @"http://schemas.xmlsoap.org/soap/envelope/";
 var unwrappedResponse = Value.Descendants((XNamespace)"http://schemas.xmlsoap.org/soap/envelope/" + "Body").First().FirstNode;

 XmlSerializer oXmlSerializer = new XmlSerializer(typeof(UserProfile));

 var responseObj = (UserProfile)oXmlSerializer.Deserialize(unwrappedResponse.CreateReader());

Eu estou seguindo esta perguntaremover / extrair cabeçalho e corpo de sabão da mensagem de sabão Mas estou recebendo um erro. Há algo de errado com este código.

questionAnswers(1)

yourAnswerToTheQuestion