Async and AWAIT

[solomem]

Asynchronous programming

Youtube tutorial Any program runs line by line, and one method has to wait for another to finish and return values.

Async is parallel.

[solomem]

dog.txt

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[solomem]

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
namespace AsyncAwaitDemo
{
    internal class Program
    {
        //Change the main method to return async task (void is returning anything)
        static async Task Main(string[] args)
        {
            string URL = "https://gist.githubusercontent.com/KenanY/7207204/raw/22563e813f1d1e4462db95786b524a16544bcedf/doge.txt";

            Stopwatch sw = new Stopwatch();

            sw.Start();

            var tasks = new List<Task> { SummonDogLocally(), SummonDogFromURL(URL) };
            await Task.WhenAll(tasks);

            sw.Stop();
            Console.WriteLine("We are done here... " + sw.Elapsed.TotalSeconds); 
        }

        // Async method has to return the Task
        // Returning a task is eqivelent to a <void> method
        // Here, we are printing the content directly inside the method.
        // If we need to return the string to the main method, we have to add the <string> to return the string

        static async Task SummonDogLocally()
        {
            Console.WriteLine("1. Summoning Dog Locally ...");

            //read all the data inside the txt file asyncly
            string dogText = await File.ReadAllTextAsync("dog.txt");

            Thread.Sleep(1000); // to show how the processes are done asynclly (in parallel)

            Console.WriteLine($"2. Dog Summoned Locally \n{dogText}");
        }
        static async Task<string> SummonDogLocallyString()
        {
            Console.WriteLine("1. Summoning Dog Locally ...");

            //read all the data inside the txt file asyncly
            string dogText = await File.ReadAllTextAsync("dog.txt");

            Console.WriteLine($"2. Dog Summoned Locally \n{dogText}");

            return dogText;
        }

        #region Summoning Dog From URL
        static async Task SummonDogFromURL(string URL)
        {
            Console.WriteLine("1. Summoning Dog From URL...");

            using(var httpClient = new HttpClient())
            {
                var response = await httpClient.GetStringAsync(URL);

                //From this line and below,
                //the execution will resume once the above awaitable is done
                //using await keyword, it will do the magic of
                //unwrapping the Task<string> into string (response variable)
                Console.WriteLine($"2. Dog Summoned Locally \n{response}");
            }
        }
        #endregion
    }
}