How to run tasks on application startup from a module

The Startup classes are used to initialize the services and piece of middleware. They are called when a tenant is initialized.

The interface OrchardCore.Modules.IModularTenantEvents provides a way to define user code that will be executed when the tenant is first hit (tenant activation).

All tenants are lazy-loaded, meaning that when the app starts the event handlers are not invoked. They are instead called when the first request is processed.

In the following example the class MyStartupTaskService inherits from ModularTenantEvents to implement IModularTenantEvents.

using System;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using OrchardCore.Modules;

public class MyStartupTaskService : ModularTenantEvents
{
    private readonly ILogger<MyStartupTaskService> _logger;

    public MyStartupTaskService(ILogger<MyStartupTaskService> logger)
    {
        _logger = logger;
    }

    public override Task ActivatingAsync()
    {
        _logger.LogInformation("A tenant has been activated.");

        return Task.CompletedTask;
    }
}

Then this class is registered on the ConfigureServices() method of the module's Startup.cs file.

services.AddScoped<IModularTenantEvents, MyStartupTaskService>();

!!! note ActivatingAsync events are invoked in the order of their registration, which is derived from the modules dependency graph. The ActivatedAsync events are invoked in the reverse order.

When ran from the terminal, you should see output like the following after the first request is processed:

info: MyStartupTaskService[0]
      A tenant has been activated.