How to Call a SignalR Hub Method from an ASP.NET Core Controller?

Calling SignalR Core Hub Method from Controller

SignalR Core provides a powerful real-time communication mechanism for ASP.NET Core applications. This article addresses the common scenario of calling a SignalR hub method from a controller.

The provided example demonstrates the need to notify connected clients upon the completion of an external operation initiated from a Windows service. Since the service cannot directly interact with SignalR, we explore two potential solutions.

Solution 1: Using IHubContext

Inject the IHubContext for the desired hub into the controller:

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

Then invoke the hub method:

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

Solution 2: Using Typed Hubs

For more granular control, create a typed client interface:

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

Inherit from the Hub class and define the client-side method:

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

Inject the typed hub context and invoke the method:

// In VarDesignCommController
[Route("api/demo")]
public class DemoController : Controller
{
    IHubContext<ChatHub, ITypedHubClient> _chatHubContext;
    public DemoController(IHubContext<ChatHub, ITypedHubClient> chatHubContext)
    {
        _chatHubContext = chatHubContext;
    }
    
    [HttpGet]
    public IEnumerable<string> Get()
    {
        _chatHubContext.Clients.All.BroadcastMessage("test", "test");
        return new string[] { "value1", "value2" };
    }
}

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