private static void AddOptionalUserProperties(XAttribute firstName, User userToAdd, XAttribute lastName,
     XAttribute email)
 {
     if (firstName != null)
     {
         userToAdd.FirstName = firstName.Value;
     }
     if (lastName != null)
     {
         userToAdd.FirstName = lastName.Value;
     }
     if (email != null)
     {
         userToAdd.FirstName = email.Value;
     }
 }
        private static User CreateUserToAdd(XElement xmlUser)
        {
            var userToAdd = new User()
            {
                Username = xmlUser.Attribute("username").Value,
                IsDeleted = xmlUser.Attribute("is-deleted").Value.Equals("1"),
                RegistrationDate = DateTime.Parse(xmlUser.Attribute("registration-date").Value),
                IpAddress = xmlUser.Attribute("ip-address").Value
            };
            var firstName = xmlUser.Attribute("first-name");
            var lastName = xmlUser.Attribute("last-name");
            var email = xmlUser.Attribute("email");

            AddOptionalUserProperties(firstName, userToAdd, lastName, email);
            return userToAdd;
        }