BizTalk SMTP The part 'PartAttachment' of message 'msg_Email' contained a null value at the end of the construct block
问题 Quick summary of issue - when I set the RawString to text, the email with attachment is sent and properly named. When I set the attachment to a RawString message, I get the error "The part 'PartAttachment' of message 'msg_Email' contained a null value at the end of the construct block." I have created my own RawString class which I have used before. The orchestration receives a CSV file via a pass-thru pipline. Following some documentation I found, I receive a XmlDocument, and in the next