WCF. IList is deserialized as array. How to make it be any writable list (ArrayList)?

Question

I have a client-server application, parts of which "talk" to each other through WCF (netTcp binding).

I have my DataContract, which has 1 field of a 3rd party class:

[Serializable]
public class MyResult{
  public ThirdPartyResult Result {get;set;}

  /* other fields */
}

Using reflection i see this:

[Serializable]
public class ThirdPartyResult {
  private IList result;

  public IList Result
  { 
    get { return result ?? (result = new ArrayList());}
  }
}

When calling the server from client I have the result as ArrayList on server. After it comes to client the result field becomes a fixed size array.

I didn't use Add service reference, but i use assembly sharing and just do

ChannelFactory<IMyContract>.CreateChannel(new NetTcpBinding("Configuration.Name"), address);

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UPDATE: the service contract

[ServiceContract]
[ServiceKnownType(typeof(ArrayList))]
[ServiceKnownType(typeof(ThirdPartyResult))]
public interface IMyContract
{
   MyResult GetResult();
}

---

Now the question:
How can I tell WCF to use ArrayList instead of Array?

---

I came up with a very bad solution (from my point of view)
Generally I wanted an ArrayList to be preserved to be able to add items to it. Finally I came up with the solution below. Yes, I know, this is completely bad, and that's why I'm still looking for some better variant.

        if (thirdParty.Results != null && thirdParty.Results.IsFixedSize)
        {
            var results = new ArrayList(thirdParty.Results);

            // Finding result by ReferenceEquals to not be tight to private variable name
            var resultsField = thirdParty.GetType()
                .GetFields(BindingFlags.Default | BindingFlags.Instance | BindingFlags.NonPublic)
                .Where(f => ReferenceEquals(f.GetValue(thirdParty), thirdParty.Results))
                .FirstOrDefault();

            if (resultsField != null)
                resultsField.SetValue(thirdParty, results);
        }
        thirdParty.AddResult(otherChild);

Answer 1

Please see the following:

WCF: Serializing and Deserializing generic collections

This solved my problem: Both the private member and custom property method work for me.

[DataMember]
private List<Person> members = new List<Person>();

OR change the property to:

[DataMember]
private Iist<Person> members = new Iist<Person>();

[DataMember()]
public IList<Person> Feedback {
    get { return m_Feedback; }
    set {
        if ((value != null)) {
            m_Feedback = new List<Person>(value);

        } else {
            m_Feedback = new List<Person>();
        }
    }
}

Answer 2

When you create a new Service Reference (or configuring an existing reference) in the Visual Studio there is a property something like "Deserialize arrays as" and there you can choose array/list/etc. You could take a look at the generated code and change your code to achieve what you want.

Answer 3

Ultimately your contract contains no information that would make it choose any particular implementation. The best way to fix this would be; to make result well-typed, perhaps as ArrayList:

private ArrayList result;
public IList Result { 
  get { return result ?? (result = new ArrayList());}
}

personally I'd hope to see a List<T> with [DataContract]/[DataMember] etc, but...

Answer 4

if nothing else then I would write an extension class to extend ThirdPartyResult

 public static class ThirdPartyResultExtension
  {
    public static ArrayList ResultsAsArrayList(this ThirdPartyResult d)
    {
      ArrayList list = new ArrayList();
      list.AddRange(d.Result);
      return list;
    }

  }

  public class ThirdPartyResult
  {
    private IList result;

    public IList Result
    {
      get { return result ?? (result = new ArrayList()); }
    }
  }

and use it like

 ThirdPartyResult r;
     ArrayList arrlist = r.ResultsAsArrayList();