File splitting and merging demo

sm.cs

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

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length < 2)
            {
                Console.WriteLine("Usage: <filename> <parts>");
                return;
            }

            var splitter = new FileSplitter.Splitter(args[0]);
            var merger = new FileSplitter.Merger(splitter.Split(Convert.ToInt32(args[1])));
            merger.Merge("_" + args[0]);
        }
    }
}

namespace FileSplitter
{
    class Splitter
    {
        private FileStream stream;

        public Splitter(string path)
        {
            this.stream = File.OpenRead(path);
        }

        private byte[] MergeParts(byte[] first, byte[] second)
        {
            byte[] merged = new byte[first.Length + second.Length];
            Array.Copy(first, merged, first.Length);
            Array.Copy(second, 0, merged, first.Length, second.Length);
            return merged;
        }

        private byte[] MakeTail(byte[] lastBuffer, int remaining)
        {
            byte[] tail = new byte[remaining];
            int readBytes = stream.Read(tail);

            if (readBytes == 0)
            {
                Array.Copy(lastBuffer, tail, remaining);
                return tail;
            }
            else
            {
                return MergeParts(lastBuffer, tail);
            }
        }

        public IEnumerable<byte[]> Split(int nparts, bool mergeLast = true)
        {
            int step = (int)this.stream.Length / nparts;
            int remaining = (int)stream.Length % nparts;
            byte[] outBuffer = new byte[step];

            while (stream.Read(outBuffer, 0, step) == step)
            {
                if (stream.Length - stream.Position < step
                    && stream.Position < stream.Length - 1
                    && mergeLast)
                    break;

                yield return outBuffer;
                Array.Fill<byte>(outBuffer, 0);
            }

            if (remaining > 0)
                yield return MakeTail(outBuffer, remaining);
        }
    }

    class Merger
    {
        IEnumerable<byte[]> parts;

        public Merger(IEnumerable<byte[]> parts)
        {
            this.parts = parts;
        }

        public void Merge(string path)
        {
            using (var stream = new FileStream(path, FileMode.Append))
            {
                foreach (var part in parts)
                    stream.Write(part, 0, part.Length);
            }
        }
    }
}