SignalR Core integration

[dotnetjunkie]

To integrate with SignalR Core, you need add the following class to your project:

NOTE: This integration requires Simple Injector >= 4.9.

using Microsoft.AspNetCore.SignalR;
using SimpleInjector.Lifestyles;

public sealed class SimpleInjectorHubActivator<T> : IHubActivator<T> where T : Hub
{
    private readonly Container container;
    private Scope scope;
	
    public SimpleInjectorHubActivator(Container container) => this.container = container;

    public T Create()
    {
        this.scope = AsyncScopedLifestyle.BeginScope(this.container);
        return this.container.GetInstance<T>();
    }

    public void Release(T hub) => this.scope.Dispose();
}

Use the following code to plug these integration points into the SignalR Core pipeline:

// Allows hubs to be registered as Scoped while having transient dependencies (not needed in >= v5.0).
container.Options.UseLoosenedLifestyleMismatchBehavior = true;

services.AddSignalR();
services.AddSimpleInjector(container, options =>
{
});

// Find all Hub implementations and register them as scoped.
var types = container.GetTypesToRegister<Hub>(typeof(MyHub).Assembly);
foreach (Type type in types) container.Register(type, type, Lifestyle.Scoped);

// NOTE: SimpleInjectorHubActivator<T> must be registered as Scoped
services.AddScoped(typeof(IHubActivator<>), typeof(SimpleInjectorHubActivator<>));

TIP: When sending SignalR messages from background threads compared to web requests, you try using IHubContext<THub> instead of the hub class itself, because the hub class, in that case, won't be fully initialized.

This next example shows this:

public class TestHandler : IHandleMessages<MessageSent>
{
    private readonly IHubContext<MyHub> _context;

    public TestHandler(IHubContext<MyHub> context)
    {
        _context = context;
    }

    public async Task Handle(MessageSent message)
    {
        await _context.Clients.All.SendAsync("sendMessage", "Message was sent!");
    }
}

This post might be updated in case we find a better way of integrating with SignalR Core.

In case you have comments or found a bug, please open a new issue.