Startup Services

What Are They?

Startup services run immediately after the dependency injection container is built. They support full constructor injection like any other service, which makes them the perfect place to hook global application events — wiring up a logout handler, warming a cache, subscribing to a message bus, or scheduling jobs.

IShinyStartupTask.Start() is intentionally synchronous. The platform does not wait for your app startup to finish, so any async work you kick off here runs in a fire-and-forget fashion. If you block for too long, the OS can kill your app before it finishes launching.

Implementing a Startup Task

using Shiny;

namespace MyApp.Infrastructure;

public class MyStartupService : IShinyStartupTask
{
    readonly ILogger<MyStartupService> logger;

    public MyStartupService(ILogger<MyStartupService> logger)
    {
        this.logger = logger;
    }

    public void Start()
    {
        // Hook global events, warm caches, etc.
        this.logger.LogInformation("App started");
    }
}

Registration

Tag the class with [Singleton] from Shiny.Extensions.DependencyInjection and call services.AddGeneratedServices() once during host build. The source generator emits a registration that exposes every interface the class implements (including IShinyStartupTask) — no reflection, AOT-clean.

using Shiny;

[Singleton]
public class MyStartupService : IShinyStartupTask
{
    // ...
}

// wherever you build your service collection
builder.Services.AddGeneratedServices();

If you prefer explicit registration:

builder.Services.AddSingleton<MyStartupService>();
builder.Services.AddSingleton<IShinyStartupTask>(sp => sp.GetRequiredService<MyStartupService>());

Either way, Start() runs automatically when the Shiny host runs.

Danger

Do not block for long inside Start(). The platform can shut your app down if startup takes too long. Kick off any slow work on a background task and return quickly.

Tip

You can combine startup services with persisted settings — define your settings class with [Bind] partial properties from Shiny.Extensions.Stores and Shiny will handle persistence; tag startup wiring with [Singleton] to register it in one go.

Tip

If your startup task also needs to react to the app entering the foreground or background, inherit from ShinyLifecycleTask instead. It implements IShinyStartupTask and the platform IApplicationLifecycle interfaces in one base class — see Lifecycle Hooks.