The task. Wait Continue.

Question

I worked on tying threads to my azure code to put things in line. For this, I used http://www.microsoft.com/download/en/details.aspx?id=19222 as a link.

my code for posting multiple posts is as follows:

public void AddMessagesAsync(IEnumerable<IQueueMessage> messages, string queue = null, TimeSpan? timeToLive = null)
{
  //check if we need to switch queues
  if (!String.IsNullOrEmpty(queue))
  {
    SetCurrent(queue);
  }

  //setup list of messages to enqueue
  var tasks = new List<Task>();
  Parallel.ForEach(messages, current => {
    if (timeToLive.HasValue)
    {
      //create task with TPL
      var task = Task.Factory.FromAsync(Current.BeginAddMessage, Current.EndAddMessage, Convert(current), timeToLive.Value, tasks); 
      //setup continuation to trigger eventhandler
      tasks.Add(task.ContinueWith((t) => AddMessageCompleted(t)));
    }
    else
    {
      //create task with TPL
      var task = Task.Factory.FromAsync(Current.BeginAddMessage, Current.EndAddMessage, Convert(current), tasks);
      //setup continuation to trigger eventhandler
      tasks.Add(task.ContinueWith((t) => AddMessageCompleted(t)));
    }
  });

  //setup handler to trigger when all messages are enqueued, a we are blocking the thread over there to wait for all the threads to complete
  Task.Factory.ContinueWhenAll(tasks.ToArray(), (t) => AddMessagesCompleted(t));               
}

private void AddMessagesCompleted(Task[] tasks)
{
  try
  {
    //wait for all tasks to complete
    Task.WaitAll(tasks);
  }
  catch (AggregateException e)
  {
    //log the exception
    var ex = e;
    //return ex;
  }

  if (AddedMessages != null)
  {
    AddedMessages(tasks, EventArgs.Empty);
  }
}

Now my question is about the task. Wait to continue (which corresponds to the document provided by MS). it seems a little strange to wait for the flows, where do you already know that they are finished? the only reason I can imagine is to clean up the errors and handle them. Did I miss something?

Answer 1

Task.WaitAll() AggregateException Task - ​​ - Task.

ContinueWhenAll() , ..

Answer 2

-, , List<T> Parallel.ForEach, , , : ConcurrentQueue<T>.

WaitAll vs ContinueWhenAll, WaitAll , - , , , , ContinuationOptions ContinueWhenAll, OnlyRanToCompeletion, , .