Introduction
When writing custom pipeline components for BizTalk Server 2006 there are times when you want to access a copy of a message, rather than the actual message being processed. Typically this is because the original data stream containing the message is not seekable, meaning that by reading the stream you prevent the next component within the pipeline from doing so.
The BizTalk Server 2006 documentation reports that the Data method of the Microsoft.BizTalk.Message.Interop.IBaseMessagePart interface provides such a facility. According to the documentation:
"In custom pipeline components, Data clones an inbound data stream, whereas GetOriginalDataStream returns the original inbound stream."
The testing I've done, however, shows that this is only the case if the original data stream is itself seekable. It seems likely that this is because a stream must be read in order to be cloned, and if it is not seekable it could never be returned to its original position following the clone. So BizTalk Server cannot honour the request to clone the stream if the stream is not seekable.
This article describes a utility method, GetSafeDataStream, which retrieves a stream which can be safely read without adversely affecting the original data stream.
Caveat: The information in this article applies to BizTalk Server 2006. Your mileage with other versions may vary.
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