关于Activator.CreateInstance解决方案

关于Activator.CreateInstance
学习三层结构，想用反射，结果单个文件里可以实现，拆成三个项目就出错，在web和DAL两个项目里都添加了BLL引用，下面是代码，还请多多指教！

namespace BLL
{
  public class CarFactory
  {
  public static ICar BuildCar()
  {
  BLL.ICar myCar = null;
  try
  {
  Type type = Type.GetType("DAL.Bus", true);
  myCar = (ICar)Activator.CreateInstance(type);
  }
  catch (TypeLoadException e)
  {
  Console.WriteLine("Unknow Car. Exception: - {0}", e.Message);
  }
  return myCar;
  }
  public static void ui()
  {
  BLL.ICar myCar = BLL.CarFactory.BuildCar();
  myCar.Say();
  }
  }

}
namespace BLL
{
  public interface ICar
  {
  void Say();
  }
}
namespace DAL
{
  public class Bus : BLL.ICar
  {
  public void Say()
  {
  Console.WriteLine("I am a Bus");
  }
  }
}
namespace Web
{
  public partial class _Default : System.Web.UI.Page
  {
  protected void Page_Load(object sender, EventArgs e)
  {
  BLL.CarFactory.ui();
  }
  }
}


[解决办法]

C# code

namespace BLL{  public interface ICar  {  void Say();  }}