using System;
using System.Threading;

namespace AsyncCallbacks
{
	class AsyncTest
	{
		[STAThread]
		static void Main(string[] args)
		{
			AsyncTest test = new AsyncTest();
			test.Run();
			Console.WriteLine();
			test.Run();

			Console.WriteLine();
			Console.WriteLine("Press <enter> to exit.");
			Console.WriteLine();
			Console.ReadLine();
		}


		private delegate void DoSomethingDelegate();
		private int startTicks;
		private DoSomethingDelegate m_delegate;
		private AsyncCallback m_callback;

		AsyncTest()
		{
			m_delegate = new DoSomethingDelegate(this.DoSomething);
			m_callback = new AsyncCallback(this.CompletionProc);
			startTicks = Environment.TickCount;
		}

		string Time
		{
			get 
			{
				return (Environment.TickCount - startTicks).ToString() + " ms";
			}
		}

		void Run() 
		{
			Console.WriteLine("About to call DoSomething at " + Time);
			IAsyncResult iar = m_delegate.BeginInvoke(m_callback, null);
			iar.AsyncWaitHandle.WaitOne();
			
			// you will get here as soon as DoSomething() finishes, but 
			// potentially before CompletionProc() has run
			
			Console.WriteLine("WaitOne finished at " + Time);
			Thread.Sleep(1200);
		}

		void DoSomething()
		{
			Console.WriteLine("Enter DoSomething at " + Time);
			Thread.Sleep(1000);
			Console.WriteLine("Exit DoSomething at " + Time);
		}

		void CompletionProc(IAsyncResult iar)
		{
			Console.WriteLine("Enter CompletionProc at " + Time);
			Thread.Sleep(1000);
			m_delegate.EndInvoke(iar);
			Console.WriteLine("Exit CompletionProc at " + Time);
		}
	}
}