public static class Ccontrol
    {
        public static void Fdo(int id, Form1 f)
        {
            Gdog Pdog = new Gdog();//这里出错~~~        }    }    public abstract class CAgame
    {
        public string name;
        public abstract void play();    }    public interface Iplay
    {
        void play();
    }    public class Gdog : CAgame,Iplay
    {
        Gdog()
        {
            name = "狗狗";
        }
        public override void play()
        {
        }
    }上面这段代码,运行后:错误 “Xiaonei_Helper.Gdog.Gdog()”不可访问,因为它受保护级别限制如果Gdog不继承CAgame就不会出错,这是什么原因呢?