Question

I am building a streaming webservice in WCF and have an issue getting access to the underlying stream.

I am implementing an existing contract based on a wsdl but I would like to make the service streaming. Since I cannot change the contract, I cannot use the Stream as a parameter option (because this changes the contract).

So I have settled on using a Message as parameter and return. This works flawlessly.

But I would like to have access to the Stream object (which must be somewhere inside the Message object or its properties). But the only thing that the Message gives me is a XmlDictionaryReader and this does not allow access to the Stream.

public Message GetMessage(Message message)
    {
        // We need some way to access the underlying stream from the message - the GetReaderAtBodyContents is not usable
        XmlDictionaryReader reader = message.GetReaderAtBodyContents();
        CopyReaderToFile(reader);
        return Message.CreateMessage(MessageVersion.Soap11, "http://tempuri.org/IStreamingService/GetMessageResponse", "Hej med dig fra GetMessage. MessageLength ");
    }

The above shows my service implementation. The major problem with the XmlDictionaryReader is that it does not give me access to the precise data sent by the client – in other words I cannot reproduce the content from the client on the service. This is bad because I then cannot verify the signature which is present in the MessageHeaders.

So is there a way of accessing the underlying stream? Can this be achieved by behaviours?

Thanks in advance

Answer 1

The problem is that streaming is not provided by message itself but by underlaying message encoder. As you can see in two methods of abstract MessageEncoder class:

• public abstract Message ReadMessage(Stream stream, int maxSizeOfHeaders, string contentType)
• public abstract void WriteMessage(Message message, Stream stream)

The stream is available only on channel level not in message. Another problem is that streaming cannot be combined with message security – so you can’t use any built-in signing etc.