C#实现装饰器模式

public class ShoppingCart  
 {
    public virtual void Show()
    {      
    }
 }

public class BaseDecorator:ShoppingCart    
{
    protected ShoppingCart _shoppingCart;

    public BaseDecorator(ShoppingCart shoppingCart)
    {
        _shoppingCart = shoppingCart;
    }

    public override void Show()
    {
        if (_shoppingCart != null)
        {
            base.Show();
        }           
    }
}

public class FruitsDecorator:BaseDecorator
{
   public FruitsDecorator(ShoppingCart shoppingCart)
       : base(shoppingCart)
   { 
   }

    public void addFruits()
    {
        Console.WriteLine("加入了水果。");
    }

    public override void Show()
    {
        base.Show();
        addFruits();
    }
}

public  class MeatsDecorator : BaseDecorator
{
   public MeatsDecorator(ShoppingCart shoppingCart)
         : base(shoppingCart)
   {
   }

   public void addMeat()
   {
       Console.WriteLine("加入了肉。");
   }

   public override void Show()
   {
        base.Show();
        addMeat();
   }
}

public class VegetablesDecorator : BaseDecorator    
{
    public VegetablesDecorator(ShoppingCart shoppingCart)
       : base(shoppingCart)
    {
    }
    public void addVegetable()
    {
        Console.WriteLine("加入蔬菜。");
    }

    public override void Show()
    {
        base.Show();
        addVegetable();
    }
}

ShoppingCart sc = new ShoppingCart();  
BaseDecorator bd = new BaseDecorator(sc);
//添加水果
FruitsDecorator fd = new FruitsDecorator(bd);
fd.Show();
//添加肉
MeatsDecorator md = new MeatsDecorator(fd);
md.Show();
//添加蔬菜
VegetablesDecorator vd = new VegetablesDecorator(md);
vd.Show();

//压缩数据
static Byte[] Compress(Byte[] data)
{
    //压缩入这个内存流
    using (MemoryStream target = new MemoryStream())
    {
        using (GZipStream gs =  new GZipStream(target,CompressionMode.Compress,true))
        {
            //把数据写入到压缩流当中
            //具体实现略
        }
         return target.ToArray();
    }
}