using System;

using System.Collections.Generic;

​

public interface IService

{

    void Execute();

}

​

public class ServiceA : IService

{

    public void Execute()

    {

        Console.WriteLine("Service A is executing.");

    }

}

​

public class ServiceB : IService

{

    public void Execute()

    {

        Console.WriteLine("Service B is executing.");

    }

}

​

public class DIContainer

{

    private readonly Dictionary<Type, Type> _services = new Dictionary<Type, Type>();

​

    public void Register<TService, TImplementation>()

    {

        _services[typeof(TService)] = typeof(TImplementation);

    }

​

    public TService Resolve<TService>()

    {

        if (_services.TryGetValue(typeof(TService), out Type implementationType))

        {

            return (TService)Activator.CreateInstance(implementationType);

        }

​

        throw new InvalidOperationException($"Service of type {typeof(TService)} is not registered.");

    }

}

​

class Program

{

    static void Main()

    {

        var container = new DIContainer();

​

        container.Register<IService, ServiceA>();

        container.Register<IService, ServiceB>();

​

        Console.WriteLine("Expected:");

        Console.WriteLine("Service A is executing.");

        Console.WriteLine("Service B is executing.\n");

        Console.WriteLine("Actual:");

        var serviceA = container.Resolve<IService>();

        serviceA.Execute();

​

        var serviceB = container.Resolve<IService>();

        serviceB.Execute();

    }

}

​