“Type not expected”, using DataContractSerializer - but it's just a simple class, no funny stuff?

Question

I\'m refactoring my XML-serialization, and figured I\'d try the DataContractSerializer. Everything runs smoothly, until it needs to serialize this class:

Answer 1

You can also combine [KnownType] and reflection to make your code more resistant to future changes.

[DataContract]
[KnownType("GetKnownPersonTypes")]
internal class Person
{
    private static IEnumerable _personTypes;

    private static IEnumerable GetKnownTypes()
    {
        if (_personTypes == null)
            _personTypes = Assembly.GetExecutingAssembly()
                                    .GetTypes()
                                    .Where(t => typeof (Person).IsAssignableFrom(t))
                                    .ToList();
        return _personTypes;
    }
}

Now a DataContractSerializer / DataContractJsonSerializer / XmlSerializer configured to work with Person, will also work with any type derived from Person (as long as it's declared within the same assembly).