Extract MTOM/XOP attachment from SOAP response using C#

Question

I'm struggling to get data (PDF document) from a SOAP response where there is an MTOM(XOP) attachment that I need to deserialize to get readable, binary data to save as a finished PDF file.

Here is the SOAP XML response what I'm receiving:

--uuid:277c111e-1c6c-4da9-9e54-95ec1073550e
Content-Type: application/xop+xml; charset=UTF-8; type="text/xml"
Content-Transfer-Encoding: binary
Content-ID: <[email protected]>

<soapenv:Envelope
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns="http://www.endpoint.com/api/">
<soapenv:Header>
    <ResponseHeader state="OK" timelasted="116"/>
</soapenv:Header>
<soapenv:Body>
    <GetDocumentResponse>
        <idDocument>1</idDocument>
        <content>
            <mime>application/pdf</mime>
            <name>document.pdf</name>
            <data fileSize="15756">
                <inc:Include
                    xmlns:inc="http://www.w3.org/2004/08/xop/include" href="cid:1234"/>
                </data>
            </content>
        </GetDocumentResponse>
    </soapenv:Body>
</soapenv:Envelope>
    
--uuid:277c111e-1c6c-4da9-9e54-95ec1073550e
Content-Type: application/pdf
Content-Transfer-Encoding: binary
Content-ID: <1234>

۞t�:�=��M��=��������۝��M��
��M��N��n��
��-��^��^���8ﮅ�n����Nt�^�랂�݅�~�략�m��^��N��~��Nt���N�M��^t�n����~��m��^��N��~��Nt�:�N��^��M��N9獴�m��M��M��݅�~�략�^�㎵��8�
��M��}��M��]�ߝ�����M��M�۽��M��݅�>��8�^�라���m��m��]��}��]��]�ߝ����M��M�۽��^x�z�^<��8���ߍ�ߝ�߭��M��}��^x�z�^7�>t�~�9�ͽ�^x�z�^w�5�nx�5�9�ͽ�M��=

This is part of code in C# (standard console app) how I sent a request:

HttpWebRequest req = (HttpWebRequest)WebRequest.Create(endpoint);
req.Headers.Add("SOAP:Action");
req.ContentType = "text/xml;charset=utf-8";
req.Method = "POST";
req.Accept = "application/pdf";
req.Headers["Authorization"] = "Basic " + Convert.ToBase64String(Encoding.Default.GetBytes("username:password"));
req.Credentials = new NetworkCredential(username, password);

var soapRequest = @"XML_Request";

using (StreamWriter writer = new StreamWriter(req.GetRequestStream()))
 {
  writer.Write(soapRequest);
 }
using (var httpResponse = (HttpWebResponse)req.GetResponse())
 {
  var streamReader = new StreamReader(httpResponse.GetResponseStream());
  result = streamReader.ReadToEnd();
 }

I read that I need to deserialize XOP and after this operation I will see readable binary data.

Even ChatGpt hasn't been able to give me valid advice on this yet.... :-)

I found some article where author tried to get the same and without comments. How to download attachment from XOP/MTOM response

I can download any Microsoft ( = official) library if it will be needed.

If I try this via SoapUI program, I'm receiving correctly desired PDF attachment (if I changed propery "Expand MTOM Attachment" and I sent request again, I saw hex string which could be easily converted to byte[] aray and saved these bytes into final PDF file.

Any suggestions how to get PDF file from the response? Ideally send please part (sample) of C# code how to continue with it.

Thank you in advance!!