Csharp/C Sharp/Language Basics/Delegate Async

Async Delegate Invocation

<source lang="csharp"> using System; using System.Collections.Generic; using System.Text; using System.Threading; public delegate int BinaryOp(int x, int y); class Program {

   static void Main(string[] args) {
       BinaryOp b = new BinaryOp(Add);
       IAsyncResult iftAR = b.BeginInvoke(10, 10, null, null);
       while (!iftAR.AsyncWaitHandle.WaitOne(2000, true)) {
           Console.WriteLine("Doing more work in Main()!");
       }
       int answer = b.EndInvoke(iftAR);
       Console.WriteLine("10 + 10 is {0}.", answer);
   }
   static int Add(int x, int y) {
       Console.WriteLine("Add() invoked on thread {0}.", Thread.CurrentThread.GetHashCode());
       Thread.Sleep(5000);
       return x + y;
   }

}

</source>

Async Delegates Callback

<source lang="csharp"> using System; using System.Threading;

class AsyncDelegatesCallback {

   public static int Add(int op1, int op2, out int result)
   {
       Thread.Sleep(1000); 
       return (result = op1 + op2);
   }
   public delegate int AddDelegate(int op1, int op2,
       out int result);
  
   public static void AnnounceSum(IAsyncResult iar)
   {
       AddDelegate add = (AddDelegate)iar.AsyncState;
  
       int result;
       add.EndInvoke(out result, iar);
  
       Console.WriteLine("[AnnounceSum] The result is {0}", result);
   }
  
   static void Main()
   {
       int result;
       AddDelegate add = new AddDelegate(Add);
       add.BeginInvoke(6, 42, out result, new AsyncCallback(AnnounceSum), add);
  
       Thread.Sleep(1000); 
   }

}

</source>

delegate BeginInvoke of IAsyncResult

<source lang="csharp"> using System; using System.Threading;

class AsyncDelegatesBlocked {

   public static int Add(int op1, int op2, out int result)
   {
       Thread.Sleep(3000);
       return (result = op1 + op2);
   }
   public delegate int AddDelegate(int op1, int op2,out int result);
  
   static void Main()
   {
       int result;
       AddDelegate add = new AddDelegate(Add);
  
       IAsyncResult iAR = add.BeginInvoke(6, 42, out result,null, null);
  
       for (int i = 0; i < 10; i++) 
       {
           Thread.Sleep(200);
           Console.Write(".");
       }
       iAR.AsyncWaitHandle.WaitOne();    
       add.EndInvoke(out result, iAR);
  
       Console.WriteLine("[Main] The result is {0}", result);
   }

}

</source>

What happens if an unhandled exception is raised in a multicast delegate?

<source lang="csharp"> using System; using System.Threading;

public delegate void DelegateClass(); public class Starter {

   public static void Main() {
       try {
           DelegateClass del = MethodA;
           IAsyncResult ar = del.BeginInvoke(null, null);
           del.EndInvoke(ar);
       } catch (Exception except) {
           Console.WriteLine("Exception caught: "+ except.Message);
       }
   }
   public static void MethodA() {
       if (Thread.CurrentThread.IsThreadPoolThread == true) {
           Console.WriteLine("Running on a thread pool thread");
       } else {
           Console.WriteLine("Running on primary thread");
       }
       throw new Exception("failure");
   }

}

</source>