AddShutdownTask.cs

using System;
using System.Threading;
using System.Threading.Tasks;

using Microsoft.Extensions.DependencyInjection;

using Orleans.Runtime;

namespace Orleans.Hosting
{
    public static class ShutdownTaskSiloBuilderExtensions
    {

        public static ISiloBuilder AddShutdownTask(
            this ISiloBuilder builder,
            Func<IServiceProvider, CancellationToken, Task> shutdownTask,
            int stage = ServiceLifecycleStage.Active)
        {
            builder.ConfigureServices(services =>
                services.AddTransient<ILifecycleParticipant<ISiloLifecycle>>(sp =>
                    new ShutdownTask(
                        sp,
                        shutdownTask,
                        stage)));
            return builder;
        }

        /// <inheritdoc />
        private class ShutdownTask : ILifecycleParticipant<ISiloLifecycle>
        {
            private readonly IServiceProvider serviceProvider;
            private readonly Func<IServiceProvider, CancellationToken, Task> func;

            private readonly int stage;

            public ShutdownTask(
                IServiceProvider serviceProvider,
                Func<IServiceProvider, CancellationToken, Task> func,
                int stage)
            {
                this.serviceProvider = serviceProvider;
                this.func = func;
                this.stage = stage;
            }

            /// <inheritdoc />
            public void Participate(ISiloLifecycle lifecycle)
            {
                lifecycle.Subscribe<ShutdownTask>(
                    stage: this.stage,
                    onStart: cancellation => Task.CompletedTask,
                    onStop: cancellation => this.func(this.serviceProvider, cancellation));
            }
        }
    }
}