Question

This is on .Net 4, full framework.

I’m trying to make a simple winforms app that will make some simple WCF REST calls. It’s using ChannelFactory and the service contract interface. Of the ~20 methods in the interface, 2 of them involve Stream (an upload and a download method) so the service side (and currently also the client side) using TransferMode=Streamed.

My goal is to include the full HTTP request and response (much like you would see in ethereal/wireshark, or fiddler, or whatever), with headers, in a textbox of the winforms app (just to show what went over the wire)

In trying to use the built-in diagnostics (via SvcConfigEditor) and my own (via implementing IClientMessageInspector and then IEndpointBehavior to add the inspector, then channelFactory.Endpoint.Behaviors.Add to add the behavior :), I’m having 2 issues:

1. When doing request.ToString() or reply.ToString() in BeforeSendRequest and AfterReceiveReply, it only gets the ‘body’ and not the headers. Digging around in the objects in the debugger it looks like the reply has them in reply.Properties[“httpResponse”], but the request’s request.Properties[“httpRequest”] has an empty Headers property even though Fiddler shows headers for Content-Type, Host, Accept-Encoding, and Connection. It seems like there’s likely a better way to get the ‘raw’ message that I’m missing (and if there’s not, someone probably knows an existing chunk of code to ‘reconstruct’ the raw one from the Message)
2. Since the transfer mode is Streamed, the ‘body’ part just shows up as the string ‘… stream …’, both in SvcTraceViewer (and the ‘raw’ svclog – even with logEntireMessage=true) and when doing a ToString(). If the mode is Buffered instead, it shows the actual body fine. I tried making a copy with reply.CreateBufferedCopy(int.MaxValue); but that then caused the actual WCF call to fail with an InvalidOperationException: This message cannot support the operation because it has been copied.

One fallback would be to move the client to Buffered and just change to StreamedRequest for the one upload call and StreamedResponse for the download call (but I’d have to do that programmatically AFAICT, as it’s set at the binding level in the config and I don’t see anyway of doing it via attributes on the calls), which would take care of the ‘body’ part and leave me with just the “get the http request headers” (issue #1, specifically request.Properties[“httpRequest”].Headers being empty) to deal with, but I’m hoping there’s some way of logging the ‘raw’ messages without doing so, leaving the TransferMode as Streamed.

Thanks!

Answer 1

I can’t find any reference right now, but it’s a known fact that you cannot capture the contents of a streamed message to WCF tracing. When streaming is enabled, only the headers of the message will be traced.

Here’s the source: Configuring Message Logging on MSDN

See towards the end of the page:

Service Level

Messages logged at this layer are
about to enter (on receiving) or leave
(on sending) user code. If filters
have been defined, only messages that
match the filters are logged.
Otherwise, all messages at the service
level are logged. Infrastructure
messages (transactions, peer channel,
and security) are also logged at this
level, except for Reliable Messaging
messages. On streamed messages, only
the headers are logged. In addition,
secure messages are logged decrypted
at this level.