public ExtensionDataObjectSerializationProxy(SerializationInfo info, StreamingContext context)
    {
        var xml = (string)info.GetValue("ExtensionData", typeof(string));

        if (!string.IsNullOrEmpty(xml))
        {
            var wrapper = DataContractSerializerHelper.LoadFromXML <ExtensionDataObjectSerializationContractProxy>(xml);
            extensionDataField = (wrapper == null ? null : wrapper.ExtensionData);
        }
        else
        {
            extensionDataField = null;
        }
    }
 public ExtensionDataObjectSerializationProxy(ExtensionDataObject extensionData)
 {
     this.extensionDataField = extensionData;
 }