.NET 6 IHubContext Dependency Injection

Question

I'm working on a simple .NET 6 application to enable data update notifications in our front-end application. I've built something similar in .NET 5 before, but I'm running across a DI issue that's got me stumped. In 5, all hubs that were mapped automatically have an IHubContext that is set up in the container for them as well. That doesn't appear to be the case anymore in 6.

System.InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNet.SignalR.IHubContext`1[SignalRNotifications.Hubs.NotificationHub]' while attempting to activate 'SignalRNotifications.Controllers.NotificationController'.

The new non-startup DI in 6 looks weird to me, but I'm just not seeing anything available that says how to fix it. Any suggestions on how to get an IHubContext to inject into my controller?

Thanks!

Update: Here is some pertinent code:

using Microsoft.AspNetCore.Builder;
using SignalRNotifications.Hubs;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
builder.Services.AddSignalR().AddAzureSignalR();


var app = builder.Build();

// Configure the HTTP request pipeline.
app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.UseRouting();
app.UseEndpoints(endpoints =>
{
    endpoints.MapHub<NotificationHub>("/NotificationHub");
});

app.Run();

Dependency injection is done in the controller in the most predictable of ways:

namespace SignalRNotifications.Controllers
{
    [AllowAnonymous]
    [Route("api/[controller]")]
    [ApiController]
    public class NotificationController : ControllerBase
    {
        private readonly IHubContext<NotificationHub> _notificationContext;

        public NotificationController(IHubContext<NotificationHub> notificationContext)
        {
            _notificationContext = notificationContext;
        }

Answer 1

System.InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNet.SignalR.IHubContext`1[SignalRNotifications.Hubs.NotificationHub]' while attempting to activate 'SignalRNotifications.Controllers.NotificationController'.

The issue might be related to you having installed the wrong version of SignalR and adding the wrong namespace reference. You are using Microsoft.AspNet.SignalR.IHubContext, instead of Microsoft.AspNetCore.SignalR.IHubContext.

According to your code and refer to the Asp.net Core SignalR document, I create a sample and inject an instance of IHubContext in a controller, everything works well. But I notice that when using the IHubContext, we need to add the using Microsoft.AspNetCore.SignalR; namespace, like this:

So, please check your code and try to use:

 using Microsoft.AspNetCore.SignalR;