andriysavin

  services.AddDecorator<IEmailMessageSender, EmailMessageSenderWithRetryDecorator>(
    decorateeServices =>
    {
        decorateeServices.AddDecorator<IEmailMessageSender, SecondEmailSenderDecorator>(
            decorateeServices2 =>
                decorateeServices2.AddScoped<IEmailMessageSender, SmtpEmailMessageSender>());
    });

andriysavin

  services.AddDecorator<IEmailMessageSender, EmailMessageSenderWithRetryDecorator>(
    decorateeServices =>
    {
        decorateeServices.AddScoped<IEmailMessageSender, SmtpEmailMessageSender>();
    });

andriysavin

var services = new ServiceCollection();

services.AddDecorator<IEmailMessageSender, EmailMessageSenderWithRetryDecorator>(
    decorateeServices => decorateeServices.AddScoped<IEmailMessageSender, SmtpEmailMessageSender>());

var serviceProvider = services.BuildServiceProvider();

var emailSender = serviceProvider.GetRequiredService<IEmailMessageSender>();

emailSender.SendMessage(new EmailMessage { Body = "Hello, decorator!" });

andriysavin

new EmailMessageSenderWithRetryDecorator(
	innerSender: new SmtpEmailMessageSender(/*dependencies*/)
	/*, other dependencies*/);

andriysavin

class EmailMessageSenderWithRetryDecorator : IEmailMessageSender
{
    private readonly IEmailMessageSender innerSender;

    // Hardcoded for simplicity.
    private const int RetryCount = 3;
    private const int DelayBetweenRetriesMs = 1000;

    public EmailMessageSenderWithRetryDecorator(
        IEmailMessageSender innerSender

andriysavin

class SmtpEmailMessageSender : IEmailMessageSender
{
    public void SendMessage(EmailMessage message)
    {
        // Put your real implementation here.
        Console.WriteLine(message.Body);
    }
}

andriysavin

interface IEmailMessageSender
{
    void SendMessage(EmailMessage message);
}

andriysavin

using System;
using System.Collections.Generic;
using System.Linq;

namespace Microsoft.Extensions.DependencyInjection
{
    public static class DecoratorServiceCollectionExtensions
    {
        public static void AddDecorator<TService, TDecorator>(
            this IServiceCollection serviceCollection,