WCF: An error while trying to serialize parameter of List / Array type

0
votes

I want to obtain avaible data contract types at run-time, that's why I'm using ServiceKnownType attribute:

[ServiceContract]
[ServiceKnownType("GetKnownTypes", typeof(KnownTypesProvider))]
public interface IService1
{
    [OperationContract]
    object GetData(bool list);
}
public static class KnownTypesProvider
{
    public static IEnumerable<Type> GetKnownTypes(ICustomAttributeProvider provider)
    {
        return new[] { typeof(CompositeType) };
    }
}

I have no problem when returning a CompositeType from GetData method, but returning a list (List<CompositeType>) or an array (CompositeType[]) causes a serialization error:

public class Service1 : IService1
{
    public object GetData(bool list)
    {
        return list ?
            // serialization error
            (object)new List<CompositeType>() :
            // successfull result
            new CompositeType();
    }
}

Error is:

There was an error while trying to serialize parameter http://tempuri.org/:GetData. The InnerException message was 'Type 'System.Collections.Generic.List`1[[WcfService2.CompositeType, WcfService2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' with data contract name 'ArrayOfCompositeType:http://schemas.datacontract.org/2004/07/WcfService2' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

I thought WCF supports collection serialization by default. Am I missing something?

How to fix this?

1
c#wcfserialization

1 Answers

0
votes

You can return List<CompositeType>() instead of object. You don't need to use the knowntype in this case.

Try changing your method to 

        public List<CompositeType> GetData1(bool list)
        {
            return new List<CompositeType>();
            // successfull result
        }