从asp.net core 2.1中的控制器访问BackgroundService

Question

I just need to access my BackgroundService from a controller. Since BackgroundServices are injected with

services.AddSingleton<IHostedService, MyBackgroundService>()

How can I use it from a Controller class?

Answer 1

最后，我在控制器中注入了IEnumerable<IHostedService> ，并按类型进行过滤： background.FirstOrDefault(w => w.GetType() == typeof(MyBackgroundService)

Answer 2

This is how I solved it:

public interface IHostedServiceAccessor<T> where T : IHostedService
{
  T Service { get; }
}

public class HostedServiceAccessor<T> : IHostedServiceAccessor<T>
  where T : IHostedService
{
  public HostedServiceAccessor(IEnumerable<IHostedService> hostedServices)
  {
    foreach (var service in hostedServices) {
      if (service is T match) {
        Service = match;
        break;
      }
    }
  }

  public T Service { get; }
}

Then in Startup :

services.AddTransient<IHostedServiceAccessor<MyBackgroundService>, HostedServiceAccessor<MyBackgroundService>>();

And in my class that needs access to the background service...

public class MyClass
{
  private readonly MyBackgroundService _service;

  public MyClass(IHostedServiceAccessor<MyBackgroundService> accessor)
  {
    _service = accessor.Service ?? throw new ArgumentNullException(nameof(accessor));
  }
}

Answer 3

Add BackgroundService in ConfigureServices function:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddHostedService<ListenerService>();


        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    }

Inject in the Controller:

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    private readonly IHostedService listenerService;

    public ValuesController(IHostedService listenerService)
    {
        this.listenerService = listenerService;
    }
}

I used BackgroundService to spin up multiple listeners for AWSSQS Listeners. If consumer wants to spin new listener then it could be done by POSTing to a Controller method (end point).