Deserialization of an array always gives an array of nulls

Question

I have a custom abstract base class with sub classes that I've made serializable/deseriablizeable with ISerializable. When I do serialization/deserialization of single instances of this class' sub classes, everything works fine. However, when I do an array of them I always end up with an array of nulls on deserialization. Serialization is done with BinaryFormatter.

The items are contained within a:

public ObservableCollection<Trade> Trades { get; private set; }

On serialization this is done in GetObjectData on the SerializationInfo parameter:

Trade[] trades = (Trade[])Trades.ToArray<Trade>();
            info.AddValue("trades", trades);

And on deserialization this is done in the serialization constructor also on the SerializationInfo parameter:

Trade[] trades = (Trade[])info.GetValue("trades", typeof(Trade[]));

            foreach (Trade t in trades)
            {
                Trades.Add(t);
            }

Deserialization always gives me an array of nulls and as I mentioned earlier, a single item serializes and deseriaizes just fine with this code:

Serialization (GetObjectData method):

info.AddValue("trade", Trades.First<Trade>());

Deserialization (Serialization Constructor):

Trade t = (Trade)info.GetValue("trade", typeof(Trade));
            Trades.Add(t);

Is this a common problem? I seem to find no occurrences of anyone else running in to it at least. Hopefully there is a solution :) and if I need to supply you with more information/code just tell me.

Thanks!

Trilogy

Hi, what is info variable? What is the format of serialization? Xml or binary? – Filipe

it's the SerializationInfo that I use in the GetObjectData and the Serialization-constructor, sorry should have mentioned that. – Trilogy

https://mcmap.net/q/483118/-c-array-xml-serialization Any help? – Maggiemaggio

What is line for Trade[] trades = (Trade[])Trades.ToArray<Trade>();? Why don't you just say var trades = Trades.ToArray(); (Linq Extension) – Filipe

Polity: I'm doing binary serialization so I don't think I have such tags available. – Trilogy

The_Smallest: For some reason I thought I had to give the types everywhere :) works without though. I'm going to test if it makes any difference in the result. EDIT: I made the Trade[] syntax change, although obviously no changes in the results. – Trilogy

Please show your Trade class (I think you have error there) – Filipe

I've run into this a couple of times now, its a right pain :( – Dragline

Answer 1

Array deserializes first. Then all inner deserialization is done. So when you try to access items, they are null.

And idea to use [OnDeserialized] Attribute on some method, that builds up all other properies. And here is example:

[Serializable]
public class TestClass : ISerializable
{
    private Trade[] _innerList;
    public ObservableCollection<Trade> List { get; set; }

    public TestClass()
    { }

    [OnDeserialized]
    private void SetValuesOnDeserialized(StreamingContext context)
    {
        this.List = new ObservableCollection<Trade>(_innerList);
        this._innerList = null;
    }

    protected TestClass(SerializationInfo info, StreamingContext context)
    {
        var value = info.GetValue("inner", typeof(Trade[]));
        this._innerList = (Trade[])value;
    }

    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        info.AddValue("inner", this.List.ToArray());
    }
}

Filipe

I'll try and look into it a bit more and supply some more code in my question. I'm actually doing serialization on a class that contains this array of serializable objects. One alternative is to serialize the whole array with different names in SerializationInfo. "trade1" and so on. – Trilogy

Updated answer, now this should help) – Filipe

Testing it out now, give me a second. You're too fast :) I didn't even get to finish my new test project :D – Trilogy

The Severe Russian programmer knows all the answers :) Thanks again! – Trilogy

@vesz I just like your questions) You ask it just on time: 2 o'clock in the morning) – Filipe

The best time to ask it seems :) – Trilogy