7.1. Asynchrony: the new approach, C#

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//7.1. Asynchrony: the new approach

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Net.Http;
using System.Threading;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //So the old approach was to subscribe to "work completed" event and call a non-blocking method.
            //Then handle result (or error) in the event handler. If you ever had to do another non-blocking call in the handler itself 
            //then you'd do the same and end up with an event handler in an event handler, i.e. messy code.
            //The new approach let's you write asynchronous code that looks like synchronous, i.e. without event handlers.
            //Besides that errors would propagate just as in synchronous code.
            
            AsyncWork(); //it's async so returns immediately, that's why we need to Sleep() below
            
            Thread.Sleep(5000);
        }
        
        public static async void  AsyncWork() //whenever you use await in the method, that method becomes async (note the modifier)
        {
            var client = new HttpClient();
            Console.WriteLine("Current thread: {0}", Thread.CurrentThread.ManagedThreadId);
            var task = client.GetStringAsync("http://stackoverflow.com"); //non-blocking, returns Task<string>
            
            //do some other work here if needed
            
            await task; //suppose now you need the downloaded string, you wait on Task<string>. 
                        //while waiting you don't run on any thread. Once task is ready some thread from
                        //thread pool will be used to execute the rest of the code.
                        //That's why this method runs on two different threads. 
            Console.WriteLine("Current thread: {0}", Thread.CurrentThread.ManagedThreadId);
            
            Console.WriteLine("Size: {0}", task.Result.Length);
        }
    }
    
        
}

Show compiler warnings [ + ] Show input
Compilation time: 0.12 sec, absolute running time: 5.4 sec, cpu time: 0.62 sec, average memory usage: 29 Mb, average nr of threads: 14