One problem with the Silverlight DataContractSerializer is that it does not maintain reference links to objects. For example: if you had a customer object "Mr Green" and 2 order objects "Cooker" & "Fire" that both held references to the (single) "Mr Green", when serialised and then deserialised using DataContractSerializer the "Cooker" would point to a different "Mr Green" than the "Fire", i.e. they are not reference equal. If this is an undesirable scenario we can choose to serialise in a binary, reference-equal way so that when we deserialise there will still only be 'one' "Mr Green".

One option is to make use of a 3rd party library such as CSLA Light. You can use CSLA Light just to enable binary serialization or you could embrace the whole CSLA architecture. Either way you will probably need to change the inheritance structure of your objects and replace any properties with CSLA properties. You can find out more about CSLA Light at http://www.lhotka.net/weblog/UsingCSLALightPart1.aspx

Example of simple CSLA

 For our Customer objects to be CSLA binary serializable we would modify the class to look something like:

    [Serializable]
    public class Customer : BusinessBase<Customer>
    {

        private static PropertyInfo<string> CustomerNameProperty = RegisterProperty<string>(new PropertyInfo<string>("CustomerName", "CustomerName", string.Empty));

        public string CustomerName
        {
            get
            {
                return GetProperty(CustomerNameProperty);   
            }
            set
            {
                
             SetProperty(CustomerNameProperty, value);   
            }
        }

We would follow a similar pattern for out order class. We could then use CSLA's MobileFormatter to serialise/deserialise (the example below defines generic methods but non-generic/typed methods could also be used):

        public static T Load<T>(Stream stream)
        {
            T m = default(T);

            Csla.Serialization.Mobile.MobileFormatter f = new Csla.Serialization.Mobile.MobileFormatter();
            m = (T) f.Deserialize(stream);

            return m;
        }


        public static void Save<T>(T obj, Stream stream)
        {
            Csla.Serialization.Mobile.MobileFormatter m = new Csla.Serialization.Mobile.MobileFormatter();
            m.Serialize(stream, obj);
        }

There are alternatives to CSLA Light for getting binary serialisation such as http://slserializelzo.codeplex.com/ although I've not investigated them as yet. (Hopefully a future version of Silverlight will allow the DataContractSerializer to output XML (albeit 'non standard') with referential links.

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