Checking whether the group is empty SignalR?

Question

In OnConnected method client is added to the group with his name (group contains all of the client id) then his name is added to the list if it is not exists.

static List<string> onlineClients = new List<string>(); // list of clients names

public override Task OnConnected()
{
    Groups.Add(Context.ConnectionId, Context.User.Identity.Name);

    if (!onlineClients.Exists(x => x == Context.User.Identity.Name))
    {
        onlineClients.Add(Context.User.Identity.Name);
    }

    return base.OnConnected();
}

In OnDisconnected method I'm trying to test whether the group is empty to remove element from list. But after removing last connection the group is not null.

public override Task OnDisconnected(bool stopCalled)
{
    if (stopCalled)
    {
        // We know that Stop() was called on the client,
        // and the connection shut down gracefully.

        Groups.Remove(Context.ConnectionId, Context.User.Identity.Name);

        if (Clients.Group(Context.User.Identity.Name) == null)
        {
            onlineClients.Remove(Context.User.Identity.Name);
        }

    }
    return base.OnDisconnected(stopCalled);
}

Can I check for empty group?

Answer 1

I think this will be a little late reply to your question, maybe you've already forgotten :d

I solved the my problem as follows using a dictionary that holds group name(User.Identity.Name) and its client numbers.

private static Dictionary<string, int> onlineClientCounts  = new Dictionary<string, int>();

public override Task OnConnected()
{
    var IdentityName = Context.User.Identity.Name;
    Groups.Add(Context.ConnectionId, IdentityName);

    int count = 0;
    if (onlineClientCounts.TryGetValue(IdentityName, out count))
        onlineClientCounts[IdentityName] = count + 1;//increment client number
    else
        onlineClientCounts.Add(IdentityName, 1);// add group and set its client number to 1

    return base.OnConnected();  
}

public override Task OnDisconnected(bool stopCalled)
{
    var IdentityName = Context.User.Identity.Name;
    Groups.Remove(Context.ConnectionId, IdentityName);

    int count = 0;
    if (onlineClientCounts.TryGetValue(IdentityName, out count))
    {
        if (count == 1)//if group contains only 1client
            onlineClientCounts.Remove(IdentityName);
        else
            onlineClientCounts[IdentityName] = count - 1;
    }

    return base.OnDisconnected(stopCalled);
}