DependencyInjection

NuGet Gallery | Microsoft.Extensions.DependencyInjection 9.0.5

dotnet add package Microsoft.Extensions.DependencyInjection

using Microsoft.Extensions.DependencyInjection;

interface IMessageService
{
    string CreateMessage();
}

class MessageService : IMessageService
{
    public string CreateMessage()
    {
        return "Hello";
    }
}

interface IMessageController
{
    void SayMessage();
}

class MessageController : IMessageController
{
    private readonly IMessageService MessageService;
    public MessageController(IMessageService messageService)
    {
        MessageService = messageService;
    }

    public void SayMessage()
    {
        Console.WriteLine(MessageService.CreateMessage());
    }
}

class Program
{
    static void Main(string[] args)
    {
        var serviceCollection = new ServiceCollection();
        serviceCollection.AddSingleton<IMessageService, MessageService>();
        serviceCollection.AddSingleton<IMessageController, MessageController>();

        var serviceProvider = serviceCollection.BuildServiceProvider();
        var messageController = serviceProvider.GetService<IMessageController>()!;

        messageController.SayMessage();
    }
}