How to send message to specific group in asp.net core using signalr?

Question

In my asp.net core 3.1 application I am using signalr for sending messages and angular for UI. So for now Everyone can see messages, I would like to send message only for appropriate organizations can see. For ex: I have 2 organizations, org1 and org2. In org1 there are 4 users and in org2 it is 5 users. I would like to send messages for ex: org1 user loggedin and only 4 users should notified. I have getCurrentOrgId as well.

My NotificationHub Class looks like:

 public class NotificationHub : Hub
    {
        public async Task SendMessage(string user, string message)
        {
            await Clients.All.SendAsync("ReceiveMessage", user, message);
        }
    }

And I am using HubContext to send message:

  private readonly IHubContext<NotificationHub> _hubContext;

  await _hubContext.Clients.All.SendAsync("ReceiveMessage",$"{notificationToAdd.ActionMessage}", cancellationToken: cancellationToken); 

// I would like some organizationGroup and send messages only loggedinuser orgId == getCurrentOrgId. Only users for appropriate organization can see notification orgId2 users should not see orgId1 users notification.

Answer 1

This is a sample of what a hub with groups might look like:

    public class NotificationHub : Hub
    {
        private readonly UserManager<ApplicationUser> userManager;

        public NotificationHub(UserManager<ApplicationUser> userManager)
        {
            this.userManager = userManager;
        }

        public async override Task OnConnectedAsync()
        {
            var user = await userManager.FindByNameAsync(Context.User.Identity.Name);

            if (user != null)
            {
                if (user.UserType == UserType.Administrator)
                {
                    await AddToGroup("Administrators");
                }
                else if (user.UserType == UserType.Employee)
                {
                    await AddToGroup("Employees");
                }
            }
            else
            {
                await Clients.Caller.SendAsync("ReceiveNotification", "Connection Error", 0);
            }
        }


        public async Task SendNotification(string group, string message, int messageType)
        {
            await Clients.Group(group).SendAsync("ReceiveNotification", message, messageType);
        }

        public async Task AddToGroup(string groupName)
        {
            await Groups.AddToGroupAsync(Context.ConnectionId, groupName);
        }

        public async Task RemoveFromGroup(string groupName)
        {
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, groupName);
        }
    }

I have an extra enum in ApplicationUser called UserType which i use to add users to groups on connect.