How to process “multipart/form-data” message submitted to BTSHttpReceive.dll


NOTE: This article is migrated from Blog AsiaTech

Date: 2009-8-27 11:05 AM

Orignal URL:


When use a form based web page as the below to submit a
XML file to one BizTalk HTTP receive location using XMLReceive pipeline, It
would fail to validate and suspended.



<FORM NAME="myForm"
ENCTYPE="multipart/form-data" METHOD="post">

<INPUT TYPE="file" NAME="myFile"

<INPUT TYPE="submit" VALUE="Upload
File" >

</FORM >



If check the suspended message, you would see the message
format similar as the below:


Content-Disposition: form-data; name="myFile";

Content-Type: text/xml







It looks like a MIME encoded message, but if develop a
customized pipeline which add a MIME/SMIME decoder before the XML disassembler,
it would fail to decode the message since actually the format is not
complete/standard MIME format.


Develop a pipeline component which is added before the
MIME/SMIME decoder at the same stage, the component would add the missed MIME
header as the below to the beginning of an incoming message to construct a
complete MIME message so the MIME/SMIME decoder can decode it, retrieve the
packed XML and pass it to the XML disassembler at the next stage in the

MIME-Version: 1.0

Content-Type: multipart/form-data;

The FixMsg pipeline component sample which is located at
the folder [BizTalk Installation Folder] \
SDK\Samples\Pipelines\CustomComponent\FixMsg can be used to add a fixed
preconfigured string to the beginning of a message. It has to be modified in
order to add a dynamic string such as boundary part as the above. The trick is
the Content-Type including boundary can be retrieved from the incoming message
context property InboundHttpHeaders. The following is the demo modified
function Execute in the FixMsg.cs which read the Content-Type head with
boundary from the context property InboundHttpHeaders and then append it to the
preconfigured prependData which is “MIME-Version: 1.0”.

public IBaseMessage Execute(IPipelineContext pc,
IBaseMessage inmsg)


IBaseMessagePart bodyPart = inmsg.BodyPart;

if (bodyPart!=null)


byte[] prependByteData = ConvertToBytes(prependData);

byte[] appendByteData = ConvertToBytes(appendData);

string headersString =

string[] headers = headersString.Split(new Char[]
{'\r','\n' }, StringSplitOptions.RemoveEmptyEntries);

string MimeHead=String.Empty;

bool Foundit=false;

for (int i=0;i<headers.Length;i++)


if (headers[i].StartsWith("Content-type:",
true, null))


MimeHead = headers[i];

Foundit = true;




if (Foundit)


StringBuilder sb = new StringBuilder();





prependByteData = ConvertToBytes(sb.ToString());


           Stream originalStrm       = bodyPart.GetOriginalDataStream();

strm = null;

(originalStrm != null)


= new FixMsgStream(originalStrm, prependByteData, appendByteData, resManager);

= strm;

strm );



return inmsg;


The following is the screen capture for the customized
pipeline project.




XiaoDong Zhu


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