// The following method can also be simply put as the 3rd param to the BeginInvoke() using Lambda expr.
static void WaitAWhileCompleted(IAsyncResult ar)
{
//The last parameter passed with the BeginInvoke() method can be read
//here using ar.AsyncState. With the WaitAWhileDelegate you can invoke the EndInvoke method to
//get the result.
WaitAWhileDelegate d2 = ar.AsyncState as WaitAWhileDelegate;
int result = d2.EndInvoke(ar);
returnString += "\nResult: " + result.ToString();
//With a callback method, you need to pay attention to the fact that this method is
//invoked from the thread of the delegate and not from the main thread.
}
// Now, using the Asynchronous Callback
public static void AsyncCallWaitAWhile()
{
returnString = String.Empty;
WaitAWhileDelegate d2 = WaitAWhile;
//The AsyncCallback delegate (third parameter of BeginInvoke()) defines a parameter of IAsnycResult
//and a void return type. Here, the address of the method WaitAWhileCompleted is assigned to the third
//parameter that fulfills the requirements of the AsyncCallback delegate. With the last parameter, you
//can pass any object for accessing it from the callback method. It is useful to pass the delegate instance
//itself, so the callback method can use it to get the result of the asynchronous method.
d2.BeginInvoke(1, 3000, WaitAWhileCompleted, d2);
returnString += "\nNow using the Asynchronous Callback:";
returnString += "\nWaiting for AsyncCallWaitAWhile()\nNumber passed = 1 and wait 3000ms\n";
int count = 0;
for (int i = 0; i < 4; i++)
{
Thread.Sleep(1000);
count++;
}
//count = count * 50; //Converting the count to represent the total ms passed.
returnString += "\nSeconds Waited: " + count.ToString();
}
