Sample of Task.Factory.FromAsync method

Program.cs

using System;
using System.IO;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        if (0 == args.Length)
            return;

        var result = ReadFileAsync(args[0]).Result;
        Console.WriteLine(result);
        Console.ReadKey();
    }

    static async Task<string> ReadFileAsync(string filePath)
    {
        if (!File.Exists(filePath))
            return null;
        
        using (var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        {
            var buff = new byte[fs.Length];

            return await Task.Factory.FromAsync(fs.BeginRead, fs.EndRead, buff, 0, buff.Length, TaskCreationOptions.None)
                .ContinueWith(_ =>
                {
                    using (var ms = new MemoryStream(buff))
                    using (var sr = new StreamReader(ms))
                        return sr.ReadToEnd();
                });
        }
    }
}

good example! It can convert BeginRead/EndRead to async/await.