After a long investigation it turns out that it looks like the [JsonObject] on top of the AdaptiveTypedElement class is not being detected. The attribute defines that classes need to be serialized as object, even though as array might be more appropriate. Because the attribute is not detected, some classes are being serialized as array, which is causing the NotImplementedException.

This is related to how DataMiner is loading DLLs into memory. What happens is the following:

1. When the AdaptiveCards DLL is loaded, it uses the attributes from Newtonsoft11, specifically the AdaptiveTypedElement with Newtonsoft11.JsonObjectAttribute.
2. Newtonsoft13 is used for serialization and looks for the NewtonSoft13.JsonObjectAttribute above classes. Since this attribute is not available (because the AdaptiveCards dll relies on the older version, Newtonsoft11), Newtonsoft13 behaves as if this attribute does not exist. Serialization continues as if theJsonObjectAttribute is not specified above the AdaptiveTypedElement class.

As a workaround you can force to serialize as object instead of array, by using a custom resolver:

private static void Test()
{
var adaptiveCardBody = new List<AdaptiveElement>()
{
new AdaptiveContainer { new AdaptiveFactSet(), }
};

var settings = new JsonSerializerSettings()
{
ContractResolver = new CustomContractResolver(),
};

var json = JsonConvert.SerializeObject(adaptiveCardBody, settings);

}
}

public class CustomContractResolver : DefaultContractResolver
{
public override JsonContract ResolveContract(Type objectType)
{
var contract = base.ResolveContract(objectType);

if (typeof(AdaptiveCollectionElement).IsAssignableFrom(contract.UnderlyingType))
{
contract = CreateObjectContract(objectType);
}

return contract;
}
}