Microsoft.Extensions.DependencyInjection Example

IDatabaseService.cs

namespace DependencyInjectionTest;

public interface IDatabaseService
{
    public void DoStuff();
}

MssqlDatabaseService.cs

namespace DependencyInjectionTest;

public class MssqlDatabaseService : IDatabaseService
{
    private string Name { get; set; }
    
    public MssqlDatabaseService(string name)
    {
        Name = name;
    }
    
    public void DoStuff()
    {
        Console.WriteLine($"Hello, my name is {Name}!");
    }
}

Program.cs

using Microsoft.Extensions.DependencyInjection;

namespace DependencyInjectionTest;

public abstract class Program
{
    public static void Main(string[] args)
    {
        var services = Startup.BuildServices();
        var databaseService = services.GetService<IDatabaseService>(); 
        databaseService?.DoStuff();
    }
}

Startup.cs

using Microsoft.Extensions.DependencyInjection;

namespace DependencyInjectionTest;

public static class Startup
{
    public static ServiceProvider BuildServices()
    {
        var services = new ServiceCollection()
            .AddSingleton<IDatabaseService>(new MssqlDatabaseService("Tester"));

        return services.BuildServiceProvider();
    }
}