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Async/Await Could Be Better

, 11 Apr 2012 CPOL 73.7K 840 58
This article will explain how the async/await pair really works and why it could be better if real cooperative threading was used instead.
using System;
using System.Threading;

namespace Pfz.Threading.Cooperative
{
	class Program
	{
		private static bool _useThreadSleep;
	
		[STAThread]
		static void Main(string[] args)
		{
			while(true)
			{
				Console.Clear();
				Console.WriteLine("This simple example will show how calls that look synchronous can");
				Console.WriteLine("work as asynchronous real cooperative threading is provided.");
				Console.WriteLine("One job will simulate reading very slow data, while another ");
				Console.WriteLine("job reads data relatively faster. With cooperative threading,");
				Console.WriteLine("They run intercalated. By simple using a normal Thread.Sleep,");
				Console.WriteLine("instead of the cooperative wait, one must first finish to allow");
				Console.WriteLine("the other start, even if it keeps most of the time waiting for data.");
				Console.WriteLine();
				Console.WriteLine("1 - See the jobs waiting in cooperative mode.");
				Console.WriteLine("2 - See the jobs waiting in non-cooperative mode.");
				Console.WriteLine("Select an option and press [ENTER]. An invalid option quits the program.");
				
			
				string option = Console.ReadLine();
				switch(option)
				{
					case "1":
						_useThreadSleep = false;
						break;
						
					case "2":
						_useThreadSleep = true;
						break;
						
					default:
						return;
				}

				DateTime begin = DateTime.Now;
				using (var jobManager = new CooperativeJobManager())
				{
					jobManager.Run(_Action);
					jobManager.Run(_Dots);
				}
				
				_event.WaitOne();
				DateTime end = DateTime.Now;
				Console.WriteLine();
				Console.WriteLine();
				Console.WriteLine("Finished.");
				Console.WriteLine("The entire process (which spend most time waiting) took: " + (end - begin));
				Console.WriteLine("Press [ENTER] to return to the main menu.");
				Console.ReadLine();
			}

		}

		private static AutoResetEvent _event = new AutoResetEvent(false);
		private static int _endCount;
		private static void _Ended()
		{
			if (_endCount == 0)
				_endCount = 1;
			else
			{
				_endCount = 0;
				_event.Set();
			}
		}
		private static void _Dots()
		{
			for(int i=0; i<100; i++)
			{
				SimulateWaitingExternalSource(100);
				Console.Write('.');
			}
			
			_Ended();
		}

		private static void _Action()
		{
			using(var reader = new DataReader())
				while(reader.ReadRecord())
					Console.WriteLine(reader.Current);
					
			_Ended();
		}
		private static void SimulateWaitingExternalSource(int time)
		{
			if (_useThreadSleep)
				Thread.Sleep(time);
			else
				CooperativeJob.Wait(time);
		}

		private sealed class DataReader:
			IDisposable
		{
			private int count;
			public bool ReadRecord()
			{
				if (count >= 10)
					return false;
					
				SimulateWaitingExternalSource(1000);
				count++;
				return true;
			}
			
			public string Current
			{
				get
				{
					return "Obtained the record " + count;
				}
			}
			
			/// <summary>
			/// This is not a real DataReader.
			/// </summary>
			public void Dispose()
			{
			}
		}
	}
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Paulo Zemek
Engineer Microsoft Corporation
United States United States
I started to program computers when I was 11 years old, as a hobbist, programming in AMOS Basic and Blitz Basic for Amiga. At 12 I had my first try with assembler, but it was too difficult at the time. Then, in the same year, I learned C and, after learning C, I was finally able to learn assembler (for Motorola 680x0). Not sure, but probably between 12 and 13, I started to learn C++. I always programmed "in an object oriented way", but using function pointers instead of virtual methods. At 15 I started to learn Pascal at school and to use Delphi. At 16 I started my first internship (using Delphi). At 18 I started to work professionally using C++ and since then I've developed my programming skills as a professional developer in C++ and C#, generally creating libraries that help other developers do they work easier, faster and with less errors. Now I just started working as a Senior Software Engineer at Microsoft. Want more info or simply want to contact me? Take a look at: http://paulozemek.azurewebsites.net/ Or e-mail me at: paulozemek@outlook.com Codeproject MVP 2012, 2015 Microsoft MVP 2013-2014

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