WCF private member reference in DataContract class becomes NULL

Question

I have a pecular problem in my WCF in the web services layer.

When I instantiate a private member (_Wagon) of my class (This instantiation is not null) in WCF, after few seconds, it's become null.

I've been trying to diagnose the problem, but no result so far.

So I'm turning to you people to help me solve this problem.

Thank you.

Hence there is my code :

[DataContract]
public class RemoteWagon
{
    private readonly IWagon _Wagon;

    public RemoteWagon(IWagon Wagon)
    {
        _Wagon = Wagon; //_Wagon isn't null here
    }

    ~RemoteWagon()
    {
        Trace.WriteLine("Do nothing");
    }       

    [DataMember]
    public RemoteBreakpoint Breakpoint
    {
        set
        {
            if (value == null)
            {
                _Wagon.Breakpoint = null; //_Wagon member is NULL...
            }
            else
            {
                //... useless code in this context.
            }
        }
    }       
}

Is all the instantiation and working with the `RemoteWagon` class happening the context of a single WCF call, or across multiple calls? — mellamokb, Apr 02 '12 at 19:24
Has the instance of `RemoteWagon` been sent across the wire from client to server between the two times you check?? Basically, WCF will **only** serialize the **public shape** of a class - everything that's marked with a `[DataMember]` attribute. Anything else will **not** be transported across the wire and thus will not be available on the other side of the communication link. — marc_s, Apr 02 '12 at 19:27

score 2 · Accepted Answer · edited May 23 '17 at 12:27

This would happen if your class had been serialized and deserialized by DataContractSerializer (for example when sending data between client and server)

Some reference: DataContractSerializer doesn't call my constructor?

If this is the case, then one possible solution, that worked for me: https://stackoverflow.com/a/9419943/724944

So a quick check&fix for this problem (I assume that you want to initialize the field yourself and not serialize it) would be to create method:

[OnDeserializing]
private void OnDeserializing(StreamingContext c)
{
    _Wagon = initializeWagon();
}

however, as you probably noticed, you won't be able to pass Wagon during deserialization - you'll have to initialize it differently.

On the other hand, If you want _Wagon serialized, then expose it as public [DataMember] property

score 1 · Answer 2 · answered Apr 02 '12 at 19:27

1

It seems that if you want _Wagon serialized you should mark it as a DataMember and ditch the "readonly" on it. If you don't want it serialized, show us your code to construct and fill this object.

answered Apr 02 '12 at 19:27

Brannon

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WCF private member reference in DataContract class becomes NULL

2 Answers2