Access SignalR Hub without Constructor Injection - asp.net-core-2.0

Question

With AspNetCore.SignalR (1.0.0 preview1-final) and AspNetCore.All (2.0.6), how can I invoke a method on a hub in server code that is not directly in a Controller and is in a class that cannot be made via Dependency Injection?
Most examples assume the server code is in a Controller and should 'ask' for the hub via an injectable parameter in a class that will created by DI.
I want to be able to call the hub's method from server code at any time, in code that is not injected. The old SignalR had a GlobalHost that enabled this approach. Basically, I need the hub to be a global singleton.
Now, everything seems to be dependent on using Dependency Injection, which is introducing a dependency that I don't want!
I've seen this request voiced in a number of places, but haven't found a working solution.
Edit
To be more clear, all I need is to be able to later access the hubs that I've registered in the Configure routine of the Startup class:
app.UseSignalR(routes =>
{
routes.MapHub<PublicHubCore>("/public");
routes.MapHub<AnalyzeHubCore>("/analyze");
routes.MapHub<ImportHubCore>("/import");
routes.MapHub<MainHubCore>("/main");
routes.MapHub<FrontDeskHubCore>("/frontdesk");
routes.MapHub<RollCallHubCore>("/rollcall");
// etc.
// etc.
});
If I register them like this:
services.AddSingleton<IPublicHub, PublicHubCore>();
it doesn't work, since I get back an uninitiated Hub.

Answer 1

No It's not possible. See "official" answer from david fowler https://github.com/aspnet/SignalR/issues/1831#issuecomment-378285819
How to inject your hubContext:
Best solution is to inject your hubcontext like IHubContext<TheHubWhichYouNeedThere> hubcontext
into the constructor.
See for more details:
Call SignalR Core Hub method from Controller

Answer 2

Thanks to those who helped with this. Here's what I've ended up on for now...
In my project, I can call something like this from anywhere:
Startup.GetService<IMyHubHelper>().SendOutAlert(2);
To make this work, I have these extra lines in Startup.cs to give me easy access to the dependency injection service provider (unrelated to SignalR):
public static IServiceProvider ServiceProvider { get; private set; }
public static T GetService<T>() { return ServiceProvider.GetRequiredService<T>(); }
public void Configure(IServiceProvider serviceProvider){
ServiceProvider = serviceProvider;
}
The normal SignalR setup calls for:
public void Configure(IApplicationBuilder app){
// merge with existing Configure routine
app.UseSignalR(routes =>
{
routes.MapHub<MyHub>("/myHub");
});
}
I don't want all my code to have to invoke the raw SignalR methods directly so I make a helper class for each. I register that helper in the DI container:
public void ConfigureServices(IServiceCollection services){
services.AddSingleton<IMyHubHelper, MyHubHelper>();
}
Here's how I made the MyHub set of classes:
using Microsoft.AspNetCore.SignalR;
using System.Threading.Tasks;
public class MyHub : Hub { }
public interface IMyHubHelper
{
void SendOutAlert(int alertNumber);
}
public class MyHubHelper : IMyHubHelper
{
public IHubContext<MyHub> HubContext { get; }
public MyHubHelper(IHubContext<MyHub> hubContext)
{
HubContext = hubContext;
}
public void SendOutAlert(int alertNumber)
{
// do anything you want to do here, this is just an example
var msg = Startup.GetService<IAlertGenerator>(alertNumber)
HubContext.Clients.All.SendAsync("serverAlert", alertNumber, msg);
}
}

Answer 3

This is a nice solution. In .NET Core 2.1 the service provider is disposed and you get cannot access disposed object. The fix is to create a scope:
public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider serviceProvider)
{
ServiceProvider = serviceProvider.CreateScope().ServiceProvider;