Question

I appear to be having an issue with the following snippet of code in that, when I come to specifying what the Item is (eg CashInHand), the actual type CashInHandPayment is not available because it hasn’t been carried across when I generate the proxy class (most likely because it doesn’t read in XmlElementAttributes).

Is there any way to force classes such as AccountPayment, CashInHandPayment and CCPayment to be serialized in the proxy class?

[DataContract]
public class Payment
{
    [XmlElementAttribute("Account", typeof(AccountPayment))]
    [XmlElementAttribute("CashInHand", typeof(CashInHandPayment))]
    [XmlElementAttribute("CreditCard", typeof(CCPayment))]
    [XmlChoiceIdentifierAttribute("ItemElementName")]
    [DataMember]
    public object Item { get; set; }
}

[DataContract]
public enum ItemElementName
{
    [EnumMember]
    Account,
    [EnumMember]
    CashInHand,
    [EnumMember]
    CreditCard
}

//This class will not be in the generated proxy class
[DataContract]
public class AccountPayment
{
    [DataMember]
    public double Amount { get; set; }
}

//classes for CashInHandPayment and CCPayment also created, but not shown.

Forgive me if ‘serialize’ isn’t the correct term to use, if you read the question and find that it isn’t, please change it accordingly!

Update – answer mentioned by Simon Svensson:

[KnownType(typeof(AccountPayment))]
[KnownType(typeof(CashInHandPayment))]
[KnownType(typeof(CCPayment))]
[DataContract]
public class Payment
{
    [XmlElementAttribute("Account", typeof(AccountPayment))]
    [XmlElementAttribute("CashInHand", typeof(CashInHandPayment))]
    [XmlElementAttribute("CreditCard", typeof(CCPayment))]
    [XmlChoiceIdentifierAttribute("ItemElementName")]
    [DataMember]
    public object Item { get; set; }
}

Many thanks, Simon!

Answer 1

Uhm. Isnt XmlElementAttribute and XmlChoiceIdentifierAttribute xml serialization, which is a older serialization compared to the DataContractSerializer which reads DataContractAttribute and DataMemberAttribute?

I believe that you should use the KnownTypeAttribute for this, but I have never tried it, nor have I had this scenario in my own code.