SingletonInitializerFactory

ISingletonInitializerFactory.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;

namespace XXX
{
    public static class SingletonExtensions
    {
        public static IServiceCollection InitEarly<T>(this IServiceCollection serviceCollection)
        {
            serviceCollection.TryAddSingleton<SingletonInitializer>();
            serviceCollection.AddSingleton<ISingletonInitializerFactory>(sp => new GenericSingletonInitializerFactory<T>(sp.GetRequiredService<T>));
            return serviceCollection;
        }
    }
    
    public interface ISingletonInitializerFactory
    {
        void Init();
    }

    class GenericSingletonInitializerFactory<T> : ISingletonInitializerFactory
    {
        private readonly Func<T> _factory;

        public GenericSingletonInitializerFactory(Func<T> factory)
        {
            _factory = factory ?? throw new ArgumentNullException(nameof(factory));
        }

        public void Init()
        {
            _factory();
        }
    }

    public class SingletonInitializer
    {
        private readonly IEnumerable<ISingletonInitializerFactory> _factories;

        public SingletonInitializer(IEnumerable<ISingletonInitializerFactory> factories)
        {
            _factories = factories;
        }

        public void Init()
        {
            foreach (var factory in _factories)
            {
                factory.Init();
            }
        }
    }
}