建造者模式

建造者模式：将一个复杂的对象的构建与他的表示分离，使得同样的构建过程可以创建不同的表示。建造者模式的好处就是使得建造代码与表示代码分离，由于建造者隐藏了该产品是如何组装的，所以如果要改变一个产品内部的表示，只需要再定义一个具体的建造者就可以了。

namespace bp
{
    class Product
    {
        List<string> parts = new List<string>();
        public void Add(string part)
        {
            parts.Add(part);
        }
        public void Show()
        {
            Console.WriteLine("Product Created");
            foreach (string item in parts)
            {
                Console.WriteLine(item);
            }
        }
    }
    abstract class Builder
    {
        public abstract void BuildPartA();
        public abstract void BuildPartB();
        public abstract Product GetResult();
    }

    class ConcreteBuilder1 : Builder
    {
        private Product product = new Product();
        public override void BuildPartA()
        {
            product.Add("Part A");
        }
        public override void BuildPartB()
        {
            product.Add("Part B");
        }
        public override Product GetResult()
        {
            return product;
        }
    }
    class ConcreteBuilder2 : Builder
    {
        private Product product = new Product();
        public override void BuildPartA()
        {
            product.Add("Part X");
        }
        public override void BuildPartB()
        {
            product.Add("Part Y");
        }
        public override Product GetResult()
        {
            return product;
        }
    }
    class Director
    {
        public void Construct(Builder bulid)
        {
            bulid.BuildPartA();
            bulid.BuildPartB();
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Director director = new Director();
            Builder b1 = new ConcreteBuilder1();
            Builder b2 = new ConcreteBuilder2();

            director.Construct(b1);
            Product p1 = b1.GetResult();
            p1.Show();

            director.Construct(b2);
            Product p2 = b2.GetResult();
            p2.Show();
        }
    }
}