protected override DateTime?Deserialize(JToken value, Type objectType)
 {
     return(value.IsNull() || value.Type.Equals(JTokenType.Null) ? null : (DateTime?)DateTimeConverter.ConvertFrom(value));
 }
 protected override JToken Serialize(DateTime?value)
 {
     return(value.HasValue ? DateTimeConverter.ConvertTo(value.Value) : null);
 }