Prototype.cs

using System;
using System.Collections.Generic;

namespace CompositePattern
{
    internal abstract class Component
    {
        protected string Name;

        protected Component(string name)
        {
            Name = name;
        }

        public abstract void Add(Component c);

        public abstract void Remove(Component c);

        public abstract void Display(int depth);
    }

    internal class Leaf : Component
    {
        public Leaf(string name) : base(name)
        {
        }

        public override void Add(Component c)
        {
            throw new System.NotImplementedException();
        }

        public override void Remove(Component c)
        {
            throw new System.NotImplementedException();
        }

        public override void Display(int depth)
        {
            Console.WriteLine($"{new string('-', depth)} {Name}");
        }
    }

    internal class Composite : Component
    {
        private readonly List<Component> _children = new List<Component>();

        public Composite(string name) : base(name)
        {
        }

        public override void Add(Component c)
        {
            _children.Add(c);
        }

        public override void Remove(Component c)
        {
            _children.Remove(c);
        }

        public override void Display(int depth)
        {
            Console.WriteLine($"{new string('-', depth)} {Name}");
            foreach (var component in _children)
            {
                component.Display(depth + 2);
            }
        }
    }
}