using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Threading;
using System.Runtime.Remoting.Messaging;

namespace AsyncDelegates
{
    class Program
    {
        delegate void MyDelegate(double width, double height, out double area, out double perimeter);

        static void Main(string[] args)
        {
            DemoPolling();
            DemoCallback();

            Console.WriteLine("Press any key to close the application...");
            Console.ReadKey();
        }


        private static void DemoPolling()
        {
            Console.WriteLine("Demonstrating Polling");
            Console.WriteLine("=====================");

            // Create a delegate and call a method asynchronously.
            MyDelegate theDel = MyAsyncMethods.RectangleCalc;
            double area, perimeter;
            IAsyncResult ar = theDel.BeginInvoke(100, 200, out area, out perimeter, null, DateTime.Now);

            // Poll until the thread has completed.
            while (!ar.IsCompleted)
            {
                Console.WriteLine("{0} and I'm still waiting", DateTime.Now);
                Thread.Sleep(TimeSpan.FromSeconds(1));
            }

            // Polling is complete, so get the method results.
            theDel.EndInvoke(out area, out perimeter, ar);

            Console.WriteLine("{0} and polling is complete.", DateTime.Now);
            Console.WriteLine("Area is {0}, perimeter is {1}", area, perimeter);
            Console.WriteLine("Object state: {0}", ar.AsyncState);
                
        }


        private static void DemoCallback()
        {
            Console.WriteLine("\nDemonstrating Callbacks");
            Console.WriteLine("=======================");

            // Create a delegate and call a method asynchronously.
            MyDelegate theDel = MyAsyncMethods.CircleCalc;
            AsyncCallback callbackDel = new AsyncCallback(MyProcessAsyncResults);
            double area, perimeter;
            IAsyncResult ar = theDel.BeginInvoke(100, 100, out area, out perimeter, callbackDel, DateTime.Now);

            // Do some work on the main thread, if there's anything to do.
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("{0} and I'm busy doing some work on the main thread", DateTime.Now);
                Thread.Sleep(TimeSpan.FromSeconds(1));
            }

            // Now just wait for the background thread to complete.
            Console.WriteLine("{0} and I don't have anything else to do, so I'll just wait...", DateTime.Now);
            ar.AsyncWaitHandle.WaitOne();

            Console.WriteLine("{0} and the background thread has finished", DateTime.Now);
        }


        // Callback method.
        private static void MyProcessAsyncResults(IAsyncResult ar)
        {
            // Downcast IAsyncResult interface into AsyncResult class type.
            AsyncResult result = (AsyncResult)ar;

            // Get our delegate from the AsyncResult object. 
            MyDelegate theDelegate = (MyDelegate)result.AsyncDelegate;

            // Get the results of the asynchronous method.
            double area, perimeter;
            theDelegate.EndInvoke(out area, out perimeter, ar);

            Console.WriteLine("{0} and the callback has been called.", DateTime.Now);
            Console.WriteLine("Area is {0}, perimeter is {1}", area, perimeter);
            Console.WriteLine("Object state: {0}", ar.AsyncState);
        }
    }
}