InfoPath Attachment Encoder Code

InfoPath-Attachment-Encoder.cs

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;
using InfoPathAttachmentEncoding;

namespace InfoPathAttachmentEncoding
{
   /// <summary>
   /// InfoPathAttachment encodes file data into the format expected by InfoPath for use in file attachment nodes.
   /// </summary>
   public class InfoPathAttachmentEncoder
   {
      private string base64EncodedFile = string.Empty;
      private string fullyQualifiedFileName;

      /// <summary>
      /// Creates an encoder to create an InfoPath attachment string.
      /// </summary>
      /// <param name="fullyQualifiedFileName"></param>
      public InfoPathAttachmentEncoder(string fullyQualifiedFileName)
      {
         if (fullyQualifiedFileName == string.Empty)
            throw new ArgumentException("Must specify file name", "fullyQualifiedFileName");
         if (!File.Exists(fullyQualifiedFileName))
            throw new FileNotFoundException("File does not exist: " + fullyQualifiedFileName, fullyQualifiedFileName);
         this.fullyQualifiedFileName = fullyQualifiedFileName;
      }

      /// <summary>
      /// Returns a Base64 encoded string.
      /// </summary>
      /// <returns>String</returns>
      public string ToBase64String()
      {
         if (base64EncodedFile != string.Empty)
            return base64EncodedFile;
         // This memory stream will hold the InfoPath file attachment buffer before Base64 encoding.
         MemoryStream ms = new MemoryStream();
         // Obtain the file information.
         using (BinaryReader br = new BinaryReader(File.Open(fullyQualifiedFileName, FileMode.Open, FileAccess.Read, FileShare.Read)))
         {
            string fileName = Path.GetFileName(fullyQualifiedFileName);
            uint fileNameLength = (uint)fileName.Length + 1;
            byte[] fileNameBytes = Encoding.Unicode.GetBytes(fileName);
            using (BinaryWriter bw = new BinaryWriter(ms))
            {
               // Write the InfoPath attachment signature. 
               bw.Write(new byte[] { 0xC7, 0x49, 0x46, 0x41 });
               // Write the default header information.
               bw.Write((uint)0x14);// size
               bw.Write((uint)0x01);// version
               bw.Write((uint)0x00);// reserved
               // Write the file size.
               bw.Write((uint)br.BaseStream.Length);
               // Write the size of the file name.
               bw.Write((uint)fileNameLength);
               // Write the file name (Unicode encoded).
               bw.Write(fileNameBytes);
               // Write the file name terminator. This is two nulls in Unicode.
               bw.Write(new byte[] {0,0});
               // Iterate through the file reading data and writing it to the outbuffer.
               byte[] data = new byte[64*1024];
               int bytesRead = 1;
               while (bytesRead > 0)
               {
                  bytesRead = br.Read(data, 0, data.Length);
                  bw.Write(data, 0, bytesRead);
               }
            }
         }

         // This memorystream will hold the Base64 encoded InfoPath attachment.
         MemoryStream msOut = new MemoryStream();
         using (BinaryReader br = new BinaryReader(new MemoryStream(ms.ToArray())))
         {
            // Create a Base64 transform to do the encoding.
            ToBase64Transform tf = new ToBase64Transform();
            byte[] data = new byte[tf.InputBlockSize];
            byte[] outData = new byte[tf.OutputBlockSize];
            int bytesRead = 1;
            while (bytesRead > 0)
            {
               bytesRead = br.Read(data, 0, data.Length);
               if (bytesRead == data.Length)
                  tf.TransformBlock(data, 0, bytesRead, outData, 0);
               else
                  outData = tf.TransformFinalBlock(data, 0, bytesRead);
               msOut.Write(outData, 0, outData.Length);
            }
         }
         msOut.Close();
         return base64EncodedFile = Encoding.ASCII.GetString(msOut.ToArray());
      }
   }
}