This is a C# source code that generates an unencrypted AS2 message with no request for an MDN.  The complete program can be downloaded at EDIINT AS2
A detailed explanation of the algorithm can be read at "Creating an AS2 client in stages".


private void btnPlain_Click(object sender, EventArgs e)
        {
            ediDocument oEdiDoc = null;
            mailDocument oMailDoc = null;
            mailMessage oMailSubject = null;

            oEdiDoc = new ediDocument();

            //object for AS2 file
            oMailDoc = oEdiDoc.GetMailDocument();

            //oject for subject/content in AS2 file
            oMailSubject = oMailDoc.GetMessageContent();

            //Create headers in the order you want them displayed
            // Put globally unique ID as Message-ID.
            oMailSubject.set_HeaderFieldValue("Message-ID", "1234567890@evalusercompany.com");  //txtMessageID.Text
            // Put AS2 version.
            oMailSubject.set_HeaderFieldValue("AS2-Version", "1.0");
            // Put AS2-To header value.
            oMailSubject.set_HeaderFieldValue("AS2-To", "ToCompanyABC");
            // Put AS2-From header value.
            oMailSubject.set_HeaderFieldValue("AS2-From", "FromCompanyXYZ");

            //add appropriate header to describe the content
            //  - "Application/EDI-X12" for EDI X12
            //  - "Application/EDIFACT" for EDI UN/EDIFACT
            //  - "Application/XML" for XML
            oMailSubject.set_HeaderFieldValue("Content-Type", "Application/EDI-X12");

            //the content that we want to send in this AS2 message is an EDI X12 file.  The file is imported into the message object.
            oMailSubject.Import(sPath + "ediFile.X12");

            //The AS2 document is constructed at this time, and the file is created. This is the file you would send by http or https
            oMailDoc.Save(sPath + @"\MailFolder\AS2PlainText.bin");

            //Send file by http
            TransmitFileByHttp(ref oMailDoc, "AS2PlainText.bin");
            
            oMailSubject.Dispose();
            oMailDoc.Dispose();
            oEdiDoc.Dispose();

            MessageBox.Show("Done");

        }
        
        

    Click here to download a trial version of the Framework EDI