Wait for notification async call

Question

I am trying to get the lync presence status of a given user. My code will talk to lync server 2010 using UCMA 4.0 in 64 bit env.

here is my code to wait for an async call to get the lync status.

private async void getNotifications(UserEndpoint endpoint, string useridSIP)
{
    _userEndpoint.PresenceServices.BeginPresenceQuery(
        new[] { useridSIP },
        new[] { "state" },
        null,
        (ar) => {
            Task<List<RemotePresentityNotification>> notificationFetch = _userEndpoint.PresenceServices.EndPresenceQuery(ar).ToList<RemotePresentityNotification>();
            List<RemotePresentityNotification> result = await notificationFetch;
            result.ForEach(x => {
                LyncUser user = new LyncUser();
                if (x.AggregatedPresenceState != null)
                {
                    user.Presence = x.AggregatedPresenceState.Availability.ToString();
                }
                else
                {
                    user.Presence = "Unknown";
                }
                user.UserName = x.PresentityUri.ToString();
                usersWithStatus.Add(user);
            });
        },
        null);
}

I am not sure how to wait till the List<RemotePresentityNotification> results are returned

Task<List<RemotePresentityNotification>> notificationFetch = _userEndpoint.PresenceServices.EndPresenceQuery(ar).ToList<RemotePresentityNotification>();
List<RemotePresentityNotification> result = await notificationFetch;

The entire source code.

using Microsoft.Rtc.Collaboration;
using Microsoft.Rtc.Collaboration.Presence;
using Oobe.Bobs.Lync.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Web;

namespace xxxx.xxxx.xxxx
{
    public class OneTimePresence
    {
        private UCMASampleHelper _helper;
        private UserEndpoint _userEndpoint;
        public List<LyncUser> usersWithStatus = new List<LyncUser>();
        public LyncPresenceChecker _checker { get; set; }
        public OneTimePresence(string useridSIP, LyncPresenceChecker checker)
        {
            _checker = checker;
            _helper = new UCMASampleHelper();
            string endpoint = String.Format("OneTime Presence query for {0}", useridSIP);
            _userEndpoint = _helper.CreateEstablishedUserEndpoint(endpoint);
            getNotifications(_userEndpoint, useridSIP);
            _helper.ShutdownPlatform();

        }
        protected void EndgetNotification(object sender, RemotePresentitiesNotificationEventArgs e)
        {
            e.Notifications.ToList<RemotePresentityNotification>().ForEach(x =>
            {
                LyncUser user = new LyncUser();
                if (x.AggregatedPresenceState != null)
                {
                    user.Presence = x.AggregatedPresenceState.Availability.ToString();
                }
                else
                {
                    user.Presence = "Unknown";
                }
                user.UserName = x.PresentityUri.ToString();
                usersWithStatus.Add(user);
            });
            _checker.Clients.All.updateLyncUserPresence(usersWithStatus);

        }

        private void getNotifications(UserEndpoint endpoint, string useridSIP)
        {
            _userEndpoint.PresenceServices.BeginPresenceQuery(
                new[] { useridSIP },
                new[] { "state" },
                EndgetNotification,
                (ar) => {
                    ar.AsyncWaitHandle.WaitOne();
                    List<RemotePresentityNotification> result = _userEndpoint.PresenceServices.EndPresenceQuery(ar).ToList<RemotePresentityNotification>();

                    result.ForEach(x =>
                    {
                        LyncUser user = new LyncUser();
                        if (x.AggregatedPresenceState != null)
                        {
                            user.Presence = x.AggregatedPresenceState.Availability.ToString();
                        }
                        else
                        {
                            user.Presence = "Unknown";
                        }
                        user.UserName = x.PresentityUri.ToString();
                        usersWithStatus.Add(user);
                    });
                },
                null);
            if (usersWithStatus.Count > 0)
            {
                _checker.Clients.All.updateLyncUserPresence(usersWithStatus);
            }

        }


    }
}

Answer 1

I believe that you are looking for the Task.Factory.FromAsync method. This method is a wrapper around the Begin and End async pattern -- detailed here. For example you'd want to do this instead:

private async Task<List<RemotePresentityNotification>> GetNotifications(UserEndpoint endpoint, string useridSIP)
{
    var task = Task.Factory.FromAsync(
        _userEndpoint.PresenceServices.BeginPresenceQuery,
        _userEndpoint.PresenceServices.EndPresenceQuery,
        new[] { useridSIP },
        new[] { "state" });

   var results = await task;
   return results.ToList();
}

1. Avoid async void detailed here
2. Use async only if there is a corresponding await

With this in place you could then await it and handle it as you see fit, like so:

private async Task SomeCaller(UserEndpoint endpoint, string useridSIP)
{
    var list = await GetNotifications(endpoint, useridSIP);
    // ... do stuff with it
}

Update 1

Consider ensuring that the PresenceServices are in fact available by checking the State as detailed here.

As long as the endpoint’s State property is set to Established, all presence services are available to it.

Additionally, this might be helpful to look at.