/* This fiddle creates a file named "File.txt" in the current directory

 * and writes the string arbitraryString into it. After that, it opens

 * a stream, reads the written string, and prints it on the console.

 * After that, it reads again but async and using the Task Parallel Library

 */

using System;

using System.IO;

using System.IO.Compression;

using System.Threading.Tasks;

​

public class Program

{

    private static string arbitraryString = @"I am 

an arbitrary

String for writing

examples";

​

    private const string FILE_NAME = "File.txt";

​

    private static string PathToFile

    {

        get

        {

            var pathToDirectory = Environment.CurrentDirectory;

            return Path.Combine(pathToDirectory, FILE_NAME);

        }

    }

​

    public static void Main()

    {

        CreateFileIfExistsAndAppendText(PathToFile, arbitraryString);

        Console.WriteLine(OpenFileAndReturnData(PathToFile));

        Parallel.Invoke(() => OpenFileAndReturnDataAync(PathToFile).Wait());

    }

​

    private static void CreateFileIfExistsAndAppendText(string path, string text)

    {

        if (!File.Exists(path))

        {

            var stream = File.Create(path);

            stream.Close();

        }

        File.AppendAllText(path, text);

    }

​

    private static string OpenFileAndReturnData(string path)

    {

        if (!File.Exists(path))

        {

            throw new FileNotFoundException();

        }

​

        var streamReader = new StreamReader(File.OpenRead(path));

        var text = streamReader.ReadToEnd();

        streamReader.Close();

        return text;

    }

​

    private static async Task<string> OpenFileAndReturnDataAync(string path)

    {

        if (!File.Exists(path))

        {

            throw new FileNotFoundException();

        }

​

        var streamReader = new StreamReader(File.OpenRead(path));

        var text = await streamReader.ReadToEndAsync();

        streamReader.Close();

        return text;

    }

}

​