DependencyInjection.cs

using System;

namespace DemoApp
{
    public class Almira
    {
        private Door Door { get; set; }
        public void LockAlmira()
        {
            this.Door.LockDoor();
        }
        public Almira(Door door)
        {
            this.Door = door;
        }

    }

    public class Door
    {
        public void LockDoor()
        {
            // Implementation
            Console.Write("Locked!");
        }
        public Door()
        {
            // Constructor
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
        	// Without Injector (Good way)
            Almira al = new Almira(new Door());
            al.LockAlmira();

            // With Injector (Not so good way)
            Injector ij = new Injector(); // However you create the injector (depends on language)
            Almira al = ij.getInstance("Almira");
            al.door.lockDoor(); // Does what the implementation tells it to
        }
    }
}