Call a hub method from a controller's action

Question

How can I call a hub method from a controller's action? What is the correct way of doing this?

Someone used this in a post:

DefaultHubManager hd = new DefaultHubManager(GlobalHost.DependencyResolver);
var hub = hd.ResolveHub("AdminHub") as AdminHub;
hub.SendMessage("woohoo");

But for me, that is throwing:

Using a Hub instance not created by the HubPipeline is unsupported.

I've read also that you can create a hub context, but I don't want to give the responsability to the action, that is, the action doing stuff like:

hubContext.Client(...).someJsMethod(..)

Answer 1

The correct way is to actually create the hub context. How and where you do that is up to you, here are two approachs:

1. Create a static method in your hub (doesn't have to be in your hub, could actually be anywhere) and then you can just call it via AdminHub.SendMessage("wooo")

   public static void SendMessage(string msg)
   {
       var hubContext = GlobalHost.ConnectionManager.GetHubContext<AdminHub>();
       hubContext.Clients.All.foo(msg);
   }
   

2. Avoid the static method all together and just send directly to the hubs clients

       var hubContext = GlobalHost.ConnectionManager.GetHubContext<AdminHub>();
       hubContext.Clients.All.foo(msg);
   

Answer 2

As per aspnet3.1

This differs from ASP.NET 4.x SignalR which used GlobalHost to provide access to the IHubContext. ASP.NET Core has a dependency injection framework that removes the need for this global singleton.

The currently suggested way to do this is by Dependency Injection. You can read more about that here.

https://learn.microsoft.com/en-us/aspnet/core/signalr/hubcontext?view=aspnetcore-3.1

---

Snippet from above

public class HomeController : Controller
{
    private readonly IHubContext<NotificationHub> _hubContext;

    public HomeController(IHubContext<NotificationHub> hubContext)
    {
        _hubContext = hubContext;
    }
}

Then call it like so

public async Task<IActionResult> Index()
{
    await _hubContext.Clients.All.SendAsync("Notify", $"Home page loaded at: {DateTime.Now}");
    return View();
}