SignalR failing to send messages to client

[NicolaiJee]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I have a web api .net 6.
I am trying to send messages to a client application.
My registration of SignalR looks this:

            services.AddSignalR(o => o.EnableDetailedErrors = true)
            .AddAzureSignalR(m => { m.ConnectionString = Configuration["AzureSignalRConnectionString"];});
    app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();

                endpoints.MapHub<ImportAssignmentHub>("/importassignmenthub");

            });

I use injection like this
IHubContext<ImportAssignmentHub> importAssignmentHub

And send messages like this

await _importAssignmentHub.Clients.Group(userName).SendAsync("SendNumberOfRows", maxRowNumber);

I have also tried to inject ImportAssignmentHub as a singleton use it directly
These events are triggered:

    public override Task OnConnectedAsync()
        {
            string name = Context.User.Identity.Name;

            name = !string.IsNullOrWhiteSpace(name) ? name : Context.User.Claims.FirstOrDefault(m => m.Type.Equals("name", StringComparison.InvariantCultureIgnoreCase))?.Value;

            if (!string.IsNullOrWhiteSpace(name))
            {
                TrackException(name + " has been connected");
            }
            return base.OnConnectedAsync();
        }
        public override Task OnDisconnectedAsync(Exception exception)
        {
            string name = Context.User.Identity.Name;

            name = !string.IsNullOrWhiteSpace(name) ? name : Context.User.Claims.FirstOrDefault(m => m.Type.Equals("name", StringComparison.InvariantCultureIgnoreCase))?.Value;
             if (!string.IsNullOrWhiteSpace(name))
            {
                TrackException(name + " has been disconnected");
            }
            return base.OnDisconnectedAsync(exception);
        }

And I can see that my username is correct.

From the live trace log in can only see this when connecting:

Any help would be greatly appriciated, as I have been trying everything for 2 days now.

Expected Behavior

No response

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

.net 6

Anything else?

No response

[rafikiassumani-msft]

@NicolaiJee Can you provide a minimal GitHub repro app? Does your code work locally without AddAzureSignalR ?

Hi @NicolaiJee. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[BrennanConroy]

I have also tried to inject ImportAssignmentHub as a singleton use it directly

Don't do that. Hubs can be registered as Transitive or not at all and SignalR will create them for you. But as a Singleton, you'll have a bunch of bugs in your application.

It looks like you're trying to invoke a method on the client using the username but using the groups feature. You should instead be using Clients.User(userName).SendAsync(...)

[NicolaiJee]

@BrennanConroy I have added ImportAssignmentHub as Transient and changed the way I try to reach the users.
I have this event

        public override Task OnConnectedAsync()
        {
            string name = Context.User.Identity.Name;

            name = !string.IsNullOrWhiteSpace(name) ? name : Context.User.Claims.FirstOrDefault(m => m.Type.Equals("name", StringComparison.InvariantCultureIgnoreCase))?.Value;

            if (!string.IsNullOrWhiteSpace(name))
            {
                TrackException(name + " has been connected");
                BroadcastMessage("11111", "test");
            }
            return base.OnConnectedAsync();
        }

And I do recieve the BroadCast message in my browser.
And I can see it in my Live Trace Tool on

But when I call this function

   public Task SendNumberOfRows(int number, string userName)
        {
            TrackException($"{number}, user {userName}, connection {Context.ConnectionId}");
            return Clients.User(userName).SendAsync("SendNumberOfRows", number);
        }

It gives me a NullReferenceException on Context.
If I remove my TrackException line is still get a NullReferenceException from my return statement.
Is something to do with my project being a WebApi?

Trying this also gives the same exception:
await Clients.All.SendAsync("SendNumberOfRows", number);

I am doing something wrong, but I don't know what.
Do I need to store the original ConnectionId and then send messages via that or ?

[NicolaiJee]

I managed to solve the connection problem.
My problem was that the username I used for sending messages was not the connectionId.
As soon as I changed that it helped me.

I found this class that just is a collection of connections:

public class ConnectionMapping<T>
    {
        private readonly Dictionary<T, HashSet<string>> _connections =
            new Dictionary<T, HashSet<string>>();

        public int Count
        {
            get
            {
                return _connections.Count;
            }
        }

        public void Add(T key, string connectionId)
        {
            lock (_connections)
            {
                HashSet<string> connections;
                if (!_connections.TryGetValue(key, out connections))
                {
                    connections = new HashSet<string>();
                    _connections.Add(key, connections);
                }

                lock (connections)
                {
                    connections.Add(connectionId);
                }
            }
        }

        public IEnumerable<string> GetConnections(T key)
        {
            HashSet<string> connections;
            if (_connections.TryGetValue(key, out connections))
            {
                return connections;
            }

            return Enumerable.Empty<string>();
        }

        public void Remove(T key, string connectionId)
        {
            lock (_connections)
            {
                HashSet<string> connections;
                if (!_connections.TryGetValue(key, out connections))
                {
                    return;
                }

                lock (connections)
                {
                    connections.Remove(connectionId);

                    if (connections.Count == 0)
                    {
                        _connections.Remove(key);
                    }
                }
            }
        }
    }

I created this class that I injected as a singleton, just to hold all active connections.
I update this collection with the OnConnected :

    public class ConnectionManager
    {
        public static readonly ConnectionMapping<string> Connections = new ConnectionMapping<string>();

    }

In my Hub I inject a HubConext like this:

 public ImportAssignmentHub(ILogger<ImportAssignmentHub> logger, IHubContext<ImportAssignmentHub> hubContext)
        {
            _logger = logger;
            _hubContext = hubContext;
        }

And then I call my methods like this:

 public async Task SendNumberOfRows(int number, string userName)
        {
            foreach (var connectionId in ConnectionManager.Connections.GetConnections(userName))
            {
                await _hubContext.Clients.Client(connectionId).SendAsync("SendNumberOfRows", number);
            }
        }

That seems to work very stable.

[NicolaiJee]

I moved my methods to another class to keep my Hub clean.