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



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” ACTION=”http://localhost/btarnhttpreceive/btshttpreceive.dll?httpmime” 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”; filename=”D:\HttpMimeTest\1.xml”

Content-Type: text/xml


<ns0:TestRoot xmlns:ns0=”http://HttpMimeTest.Schema1″>







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 pipeline.



MIME-Version: 1.0

Content-Type: multipart/form-data; boundary=—————————7d91593580102



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 = inmsg.Context.Read(“InboundHttpHeaders”, “”).ToString();

                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();

                   Stream strm = null;


                   if (originalStrm != null)


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

                             bodyPart.Data    = strm;

                             pc.ResourceTracker.AddResource( strm );




            return inmsg;



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




XiaoDong Zhu 



Comments (1)

  1. Anu says:

    Very very clear and helpful! thanks a lot! Saved Me a lot of time and trouble!!!

    Minor change that I had to make was modify 'Content-type:' to 'Content-Type:' in the code modification.Thanks a lot!