HttpSessionState not available during SignalR.PersistentConnection.OnConnected event

Question

I am using SignalR for pushing messages from an ASP.NET MVC server to web clients.

I want to store the connection Id of the current client when a new connection from a client has been accepted, so that when I want to send data to this specific client, I can retrieve its connection Id from the Session and send it the message.

However, in the OnConnected event handler, the session is null. As a result, my code throws a null reference exception when I try to put the connectionId in the session.

Here's the code snippet.

using Microsoft.AspNet.SignalR;

namespace TestSignalR
{
    public class SignalRServerListener : PersistentConnection
    {
        protected override System.Threading.Tasks.Task OnConnected(
                                          IRequest request, 
                                          string connectionId)
        {
            System.Diagnostics.Debugger.Break();

            System.Diagnostics.Debug.
             Print("Connection request received and accepted from 
             client with connection Id {0}", connectionId);

            HttpContext.Current.Session["connectionId"] = connectionId;

            return base.OnConnected(request, connectionId);
        }
    }
}

wwcdwdcw wwcdwdcw · Accepted Answer · 2013-05-28T17:27:54

You can track the clients like below

class MyConnections
{
    private static List<String> _MyClients = new List<String>();

    public override Task OnConnected()
    {
        _MyClients.Add(Context.ConnectionId);
        return base.OnConnected();
    }

    public override Task OnDisconnected()
    {
        _MyClients.Remove(Context.ConnectionId);
        return base.OnDisconnected();
    }

    public static bool IsConnected(string cid)
    {
        return _MyClients.Contains(cid);
    }
}

Now, when the server wants to send data to one of those clients, how should the server know which connection Id should be used in the Context.Connection.Send(connectionId, message)?

Context.DefaultSignal

HttpSessionState not available during SignalR.PersistentConnection.OnConnected event

1 Answers