Slicing File

namespace SlicingFile
{
    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;

    public class SlicingFile
    {
        public static void Main()
        {
            const string SourceFilePath = @"../../source.mp4";
            const string DestinationFolder = @"../../Slices";

            Console.Write("Enter the number of slices: ");
            int numberOfSlices = int.Parse(Console.ReadLine());

            Slice(SourceFilePath, DestinationFolder, numberOfSlices);

            List<string> fileNames = Directory.GetFiles(DestinationFolder).ToList();

            Assemble(fileNames, "../../");
        }

        private static void Slice(string sourceFilePath, string destinationDirectory, int numberOfSlices)
        {
            using (var source = new FileStream(sourceFilePath, FileMode.Open))
            {
                int bytesPerFile = (int)(source.Length / numberOfSlices);
                int remainingBytes = (int)(source.Length % numberOfSlices);
                string fileExtension = Path.GetExtension(source.Name);

                for (int fileIndex = 0; fileIndex < numberOfSlices; fileIndex++)
                {
                    string fileName = string.Format("File-{0}{1}", fileIndex, fileExtension);
                    string destinationPath = destinationDirectory + "/" + fileName;

                    var bytesToWrite = fileIndex == numberOfSlices - 1 ? remainingBytes : bytesPerFile;

                    byte[] buffer = new byte[bytesToWrite];

                    using (var destination = new FileStream(destinationPath, FileMode.Create))
                    {
                        source.Read(buffer, 0, bytesToWrite);
                        destination.Write(buffer, 0, bytesToWrite);
                    }
                }
            }
        }

        private static void Assemble(List<string> files, string destinationDirectory)
        {
            const int DefaultBufferSizeInBytes = 4096;

            string extension = files[0].Substring(files[0].LastIndexOf('.'));
            string path = destinationDirectory + "assembled" + extension;

            using (var assembled = new FileStream(path, FileMode.Append, FileAccess.Write))
            {
                byte[] buffer = new byte[DefaultBufferSizeInBytes];

                foreach (var file in files)
                {
                    using (var slice = new FileStream(file, FileMode.Open))
                    {
                        while (true)
                        {
                            int bytesRead = slice.Read(buffer, 0, DefaultBufferSizeInBytes);

                            if (bytesRead == 0)
                            {
                                break;
                            }

                            assembled.Write(buffer, 0, bytesRead);
                        }
                    }
                }
            }
        }
    }
}