using System;

using System.IO;

using System.Threading.Tasks;

public class Program

{

    static void Main(string[] args)

    {

        var read1 = ReadFileAsync(@"C:\Users\stefan.stoykov\Desktop\file.txt");

        var read2 = ReadFileAsync(@"C:\Users\stefan.stoykov\Desktop\file2.txt");

        Task.WhenAll(read1,read2)

            .ContinueWith(task=> Console.WriteLine("All files have been read successfuly"));

        Console.ReadLine();

    }

    private static Task<int> ReadFileAsync(string filePath)

    {

        var fs = File.OpenRead(filePath);

        var readBuffeer = new byte[fs.Length];

        var readTask = fs.ReadAsync(readBuffer, 0, (int)fs.Length);

        readTask.ContinueWith(task=>

                              {

                                  if(task.Status == TaskStatus.RanToCompletion)

                                      Console.WriteLine("Read {0} bytes successfulyf from file {1}", task.Result, filePath);

                                  else

                                      Console.WriteLine("Exception occured wbihle reading the file {0}", filePath);

                                  fs.Dispose();

                              });

        return readTask;

    }

​