Question

I have a hub with method that is called client-side. This method launches a timer with a delegate that runs every 10 seconds. Since it wouldn’t make sense to keep running this delegate if no one is connected to the hub, I want to check if any users are still connected from inside the delegate before I reschedule it. Is there any way to do this?

Answer 1

Probably the most used solution is to keep a static variable containing users currently connected and overriding OnConnect and OnDisconnect or implementing IDisconnect depending on the version that you use.

You would implement something like this:

public class MyHub : Hub
{
    private static List<string> users = new List<string>();
    public override Task OnConnected()
    {
        users.Add(Context.ConnectionId);
        return base.OnConnected();
    }

    //SignalR Verions 1 Signature
    public override Task OnDisconnected()
    {
        users.Remove(Context.ConnectionId);
        return base.OnDisconnected();
    }

    //SignalR Version 2 Signature
    public override Task OnDisconnected(bool stopCalled)
    {
        users.Remove(Context.ConnectionId);
        return base.OnDisconnected(stopCalled);
    }

    // In your delegate check the count of users in your list.
}