WCF call using HttpWebRequest access datamemebers and datacontract class

From stream on in your code? The object comes deserialized with the use of DataContractSerializer, please see. It is controlled by [DataMember] attributes and does not require anything, not even access modifiers. Please see:
http://msdn.microsoft.com/en-us/library/ms733127%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.runtime.serialization.datacontractserializer(v=vs.110).aspx[^].

If you need to access something from your semantic code, you need to make a property (properties) for that, or add internal or public access modifier to existing property (properties). Internal for access from the same assembly, public for access from other (referencing) assemblies. Please see:
http://msdn.microsoft.com/en-us/library/ms173121.aspx[^],
Conversion failed when converting date and/or time from character string.?[^],
http://msdn.microsoft.com/en-us/library/aa288470%28v=vs.71%29.aspx[^],
http://msdn.microsoft.com/en-us/library/vstudio/x9fsa0sw%28v=vs.110%29.aspx[^].

—SA