using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

            var builder = new BurgerBuilder()

                .WithBread()

                .WithSauce().WithChili().Build()

                .WithBeef()

                .WithSauce().WithCurry().Build()

                .WithBread()

                .Build();

    }

    public class BurgerBuilder

    {

        private List<object> ingredients;

        public BurgerBuilder()

        {

            ingredients = new List<object>();

        }

        public BurgerBuilder WithBread()

        {

            ingredients.Add("Bread");

            return this;

        }

​

        public BurgerBuilder WithBeef()

        {

            ingredients.Add("Beef");

            return this;

        }

​

        public SauceBuilder WithSauce()

        {

            var sauce = new SauceBuilder(this);

            ingredients.Add(sauce);

            return sauce;

        }

​

        public BurgerBuilder Build()

        {

            // use ingredients

            return this;

        }

​

        public class SauceBuilder

        {

            private readonly BurgerBuilder burgerBuilder;

            public SauceBuilder(BurgerBuilder burgerBuilder)

            {

                this.burgerBuilder = burgerBuilder;

            }

            public SauceBuilder WithCurry()

            {

                burgerBuilder.ingredients.Add("Curry");

                return this;

            }

​

            public SauceBuilder WithChili()

            {

                burgerBuilder.ingredients.Add("Chili");

                return this;

            }

​

            public BurgerBuilder Build()

            {

                return burgerBuilder;

            }

        }

    }

}