Question

When a page loads I start a new task in my hub. This task sends data to a browser updating a certain html elements. When I browse away from the page I want to stop the task.

The problem is that before the task is stopped (due to it’s sleep argument), a new tokenSource = new CancellationTokenSource();
is set before the previous instance of this task had a chance to stop.

What i’m trying to do is to have the task stop when browsing away from the page to a different page that is not requiring signalR. BUT maybe, not stop it if it’s only a refresh of the same page. Not sure how to do it. To sum it up, I want to guarantee that only 1 instance of this task is running (AND only on the page that requires it/or have a listener)
any info greatly appreciated.
thanks

CODE:

public class TaskActionStatus : Hub
{
    #region Static Fields

    /// <summary>
    /// The token source.
    /// </summary>
    private static CancellationTokenSource tokenSource;

    /// <summary>
    /// The url string.
    /// </summary>
    private static string url = string.Empty;

    #endregion

    #region Public Methods and Operators

    /// <summary>
    /// The get tasks status.
    /// </summary>
    /// <param name="siteId">
    /// The site id.
    /// </param>
    /// <param name="location"></param>
    public void GetTasksStatus(int? siteId)
    {
        var taskRepository = UnityContainerSetup.Container.Resolve<ITaskRepository>();

        tokenSource = new CancellationTokenSource();
        CancellationToken ct = tokenSource.Token;

        // init task for checking task statuses
        var tasksItem = new DownloadTaskItem();

        // start task only if at least one listener
        if (UserHandler.ConnectedIds.Count < 2 && !taskRepository.IsTasksStatusAsyncRunning())
        {
            taskRepository.GetTasksStatusAsync(siteId, tasksItem, ct);

            // subscribe to event [ listener ]
            tasksItem.Changed += this.UpdateTasksStatus;
        }
        else tokenSource.Cancel();
    }

    /// <summary>
    /// The on connected.
    /// </summary>
    /// <returns>
    /// The <see cref="Task"/>.
    /// </returns>
    public override Task OnConnected()
    {
        UserHandler.ConnectedIds.Add(this.Context.ConnectionId);
        return base.OnConnected();
    }

    /// <summary>
    /// The on disconnected.
    /// </summary>
    /// <returns>
    /// The <see cref="Task"/>.
    /// </returns>
    public override Task OnDisconnected()
    {
        UserHandler.ConnectedIds.Remove(this.Context.ConnectionId);
        if (UserHandler.ConnectedIds.Count == 0)
        {
            try
            {
                    tokenSource.Cancel();
            }
            catch (Exception ex)
            {
                Log.Error(ex);
            }
        }

        return base.OnDisconnected();
    }

    /// <summary>
    /// The update tasks status.
    /// </summary>
    /// <param name="sender">
    /// The sender.
    /// </param>
    /// <param name="e">
    /// The e.
    /// </param>
    public void UpdateTasksStatus(object sender, TaskEventArgs e)
    {
        this.Clients.All.updateMessages(e.Tasks);
    }

    #endregion
}

/// <summary>
/// The user handler.
/// </summary>
public static class UserHandler
{
    #region Static Fields

    /// <summary>
    /// The connected ids.
    /// </summary>
    public static HashSet<string> ConnectedIds = new HashSet<string>();

    #endregion
}


    public bool IsTasksStatusAsyncRunning()
    {
        if (tasksStatusAsync != null && tasksStatusAsync.Status.Equals(TaskStatus.Running))
        {
            return true;
        }

        return false;
    }

Answer 1

Moving this line:

            tokenSource = new CancellationTokenSource();
            CancellationToken ct = tokenSource.Token;

…
making it this:

       if (UserHandler.ConnectedIds.Count < 2)
        {
            Trace.WriteLine("GetTasksStatus: Starting new task");

            tokenSource = new CancellationTokenSource();
            CancellationToken ct = tokenSource.Token;

            taskRepository.GetTasksStatusAsync(siteId, tasksItem, ct);

            // subscribe to event [ listener ]
            tasksItem.Changed += this.UpdateTasksStatus;
        }

did it for me. thanks