C# StreamReader ReadToEndAsync

[ComVisibleAttribute(false)]
[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public override Task<string> ReadToEndAsync()

using System;/*from  www .  j  a v a2  s  . c o  m*/
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        ReadCharacters();
    }

    static async void ReadCharacters()
    {
        String result;
        using (StreamReader reader = File.OpenText("existingfile.txt"))
        {
            result = await reader.ReadToEndAsync();
            Console.WriteLine(result);
        }
    }
}