C#

public Microsoft.BizTalk.Message.Interop.IBaseMessage Execute(Microsoft.BizTalk.Component.Interop.IPipelineContext pc, Microsoft.BizTalk.Message.Interop.IBaseMessage inmsg)
        {
            // 
            // TODO: implement component logic
            // 
            
            IBaseMessagePart bodyPart = inmsg.BodyPart;
            IBaseMessage outmsg = null;
            Stream inStream;
            MemoryStream outStream = new MemoryStream();
            byte[] inBuffer;
            byte[] thefilename;
            byte[] outBuffer;
            object tempObj;
            string msgString = "";
            //int endpos = 0;
            string fileName = "";
            string fullPath = "";

            if (bodyPart != null)
            {
                tempObj = inmsg.Context.Read("ReceivedFileName", "http://schemas.microsoft.com/BizTalk/2003/file-properties");
                if (tempObj != null)
                    fullPath = tempObj.ToString();
                else
                    return inmsg;
                //The filename is to be added to the end of the stream.
                fileName = "*" + System.IO.Path.GetFileName(fullPath) + "\r\n";

                thefilename = ConvertToBytes(fileName);
                inStream = bodyPart.GetOriginalDataStream();
                
                //Define lengths for memory and byte array
                Int32 inStreamLength = Convert.ToInt32(inStream.Length);
                Int32 FileNameLength = Convert.ToInt32(thefilename.Length);
                Int32 TotalBufferLength = Convert.ToInt32(inStreamLength) + Convert.ToInt32(FileNameLength);

                inBuffer = new byte[TotalBufferLength];
                inStream.Read(inBuffer, 0, inStreamLength);
                
                int count = inStreamLength;
                int j = 0;
                while (count < TotalBufferLength)
                {
                    inBuffer[count++] = thefilename[j++];   //Convert.ToByte(inStream.ReadByte());
                }

                outStream.Write(inBuffer, 0, TotalBufferLength);
                outStream.Seek(0, SeekOrigin.Begin);
                bodyPart.Data = outStream;

                //Build a new message, do no just change the bodypart.  Recommended by MS
                outmsg = cloneIBaseMessage(pc.GetMessageFactory(), inmsg, outStream);
                return outmsg;
            }
            else
                return inmsg;
        }