Efficient reading and writing of files should just be a
matter of using huge buffers.

I would be more worried about whether PDF files
can just be concatenated.

Arne

Well, you don't really need the fastest way.  You need a reasonably fast
way.  Just use System.IO.FileStream, open one for your output file, and
iterate over your input files.  For each input file, read a buffer from the
input file, write the buffer to the output file, repeat.

You don't need to use huge buffers, and it's probably not worth while to use
async IO or double buffering or any of that.

Here's a simple file concatenation program:

David

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace FileConcat
{
 class Program
 {
   static int Main(string[] args)
   {
     if (args.Length != 2)
     {
       Console.WriteLine("usage FileConcat [SourceDir] [DestinationFile]");
     }
     try
     {
       Run(args[0],args[1]);
       return 0;
     }
     catch (Exception ex)
     {
       Console.WriteLine(ex);
       return 1;
     }
   }
   static void Run(string SourceDir, string OutputFileName)
   {
     string[] inputFiles = Directory.GetFiles(SourceDir);

     int bufSize = 1024 * 64;

     byte[] buf = new byte[bufSize];

     using (FileStream outFile =
       new FileStream(OutputFileName, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.None, bufSize))
     {
       foreach (string inputFile in inputFiles)
       {
         using (FileStream inFile =
           new FileStream(inputFile, FileMode.Open, FileAccess.Read,
FileShare.Read, bufSize))
         {
           int br = 0;
           while ((br = inFile.Read(buf,0,buf.Length))> 0)
           {
             outFile.Write(buf,0,br);
           }
         }
       }
     }

   }
 }
}