Derived Class对象如何添加到Base Class对象List

Question

鉴于以下代码,我从Shape继承了一个Circle:

class Shape
{
    void Draw();
}

class Circle : Shape
{
}

void Main(string[] args)
{
    Shape s = new Shape();
    Shape s2 = new Shape();
    Circle c = new Circle();

    List<Shape> ShapeList = new List<Shape>();

    ShapeList.Add(s);
    ShapeList.Add(s2);
    ShapeList.Add(c);
}

怎么可以c加入ShapeList？

Answer 1

A Circle 是a Shape,因为Circle扩展Shape.因此,您可以始终将Circle对象视为一个对象,Shape因为我们可以绝对确定可以在a上执行的所有操作也可以在a Shape上执行Circle.