While the TPL has explicit wrappers for the asynchronous programming model (APM) that you can read about here: TPL APM Wrappers, there is no explicit way to manage events.
I usually hide the "muck" of subscribing and waiting for a completed action in events with a callback. For example, the following method generates a random number. I'm using a delay to simulate a service call and a thread task to make the call back asynchronous: you call into the method, then provide a delegate that is called once the information is available.
private static void _GenerateRandomNumber(Action<int> callback)
{
var random = _random.Next(0, 2000) + 10;
Console.WriteLine("Generated {0}", random);
Task.Factory.StartNew(() =>
{
Thread.Sleep(1000);
callback(random);
}, TaskCreationOptions.None);
}
Now consider an algorithm that requires three separate calls to complete to provide the input values in order to compute a result. The calls are independent so they can be done in parallel. The TPL supports "parent" tasks that wait for their children to complete, and a first pass might look like this:
private static void _Incorrect()
{
var start = DateTime.Now;
int x = 0, y = 0, z = 0;
Task.Factory.StartNew(
() =>
{
Task.Factory.StartNew(() => _GenerateRandomNumber(result => x = result),
TaskCreationOptions.AttachedToParent);
Task.Factory.StartNew(() => _GenerateRandomNumber(result => y = result),
TaskCreationOptions.AttachedToParent);
Task.Factory.StartNew(() => _GenerateRandomNumber(result => z = result),
TaskCreationOptions.AttachedToParent);
}).ContinueWith(t =>
{
var finish = DateTime.Now;
Console.WriteLine("Bad Parallel: {0}+{1}+{2}={3} [{4}]",
x, y, z,
x+y+z,
finish - start);
_Parallel();
});
}
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