Call SignalR Core Hub method from Controller

Question

How can I call SignalR Core Hub method from Controller?
I am using ASP.NET Core 2.0 with Microsoft.AspNetCore.SignalR (1.0.0-alpha2-final).

I have windows service which communicate with Excel, SolidEdge ... When operation is complete it post request to my controller in ASP.NET Core application. Now I need to inform all clients connected to server with SignalR that external program completed some task.
I can not change the way window service works. (Can not connect to SignalR from window service).
I found plenty solution for old SignalR (GlobalHost.ConnectionManager.GetHubContext), but much has changed and those solutions are not working anymore.

My controller:

[Route("API/vardesigncomm")]
public class VarDesignCommController : Controller
{
    [HttpPut("ProcessVarDesignCommResponse/{id}")]
    public async Task<IActionResult> ProcessVarDesignCommResponse(int id)
    {
        //call method TaskCompleted in Hub !!!! How?

        return new JsonResult(true);
    }
}

My hub:

public class VarDesignHub : Hub
{
    public async Task TaskCompleted(int id)
    {
        await Clients.All.InvokeAsync("Completed", id);
    }
}

Answer 1

Solution 1

Another possibility is to inject your HubContext into your controller like:

public VarDesignCommController(IHubContext<VarDesignHub> hubcontext)
{
    HubContext = hubcontext;
    ...
}

private IHubContext<VarDesignHub> HubContext
{ get; set; }

Then you can also call

await this.HubContext.Clients.All.InvokeAsync("Completed", id);

But then you will direct call methods on all clients.

Solution 2

You can also work with typed hubs: Simple create an interface where you define which methods your server can call on the clients:

public interface ITypedHubClient
{
    Task BroadcastMessage(string name, string message);
}

Inherit from Hub:

public class ChatHub : Hub<ITypedHubClient>
{
    public void Send(string name, string message)
    {
        Clients.All.BroadcastMessage(name, message);
    }
}

Inject your the typed hubcontext into your controller, and work with it:

[Route("api/demo")]
public class DemoController : Controller
{
    IHubContext<ChatHub, ITypedHubClient> _chatHubContext;
    public DemoController(IHubContext<ChatHub, ITypedHubClient> chatHubContext)
    {
        _chatHubContext = chatHubContext;
    }

    // GET: api/values
    [HttpGet]
    public IEnumerable<string> Get()
    {
        _chatHubContext.Clients.All.BroadcastMessage("test", "test");
        return new string[] { "value1", "value2" };
    }
}