Is there a reason why a base class decorated with XmlInclude would still throw a type unknown exception when serialized?

Question

I will simplify the code to save space but what is presented does illustrate the core problem.

I have a class which has a property that is a base type. There are 3 d

Answer 1

I had the same issue and some Googling lead me here. I could not accept to have the XMLInclude attribute for each implementation in the base class. I got it to work with a generic serialization method. First off, some of the OP's original example, but slightly modified for clarity:

public abstract class PaymentSummary
{
  public string _summary;
  public string _type;
}

public class xPaymentSummary : PaymentSummary
{
  public xPaymentSummary() { }

  public xPaymentSummary(string summary)
  {
     _summary = summary;
     _type = this.GetType().ToString();
  }
}

In addition to the above, there is also a yPaymentSummary and zPaymentSummary with exactly the same implementation. These are added to a collection, and then the serialization method can be called on each:

List summaries = new List();
summaries.Add(new xPaymentSummary("My summary is X."));
summaries.Add(new yPaymentSummary("My summary is Y."));
summaries.Add(new zPaymentSummary("My summary is Z."));

foreach (PaymentSummary sum in summaries)
  SerializeRecord(sum);

Finally, the serialization method - a simple generic method, that uses the Type of record when serializing:

static void SerializeRecord(T record) where T: PaymentSummary
{
  var serializer = new XmlSerializer(record.GetType());
  serializer.Serialize(Console.Out, record);

  Console.WriteLine(" ");
  Console.WriteLine(" ");
}

The above yields the following output: