private void button4_Click(object sender, EventArgs e)
{
HandleClass6 h = new HandleClass6();
Class7 c7 = new Class7();
//Class6 parent = c7;
//h.GetClass6String(parent);
MessageBox.Show( h.GetClass6String(c7));
}
private void button3_Click(object sender, EventArgs e)
{
Class6 parent;
Class7 c7 = new Class7();
parent = c7; //上溯造型,父类（接口）变量指向子类对象。
MessageBox.Show(parent.GetString());
MessageBox.Show(parent.GetStringEx());
//Class8 c8 = new Class8();
//parent = c8;
//MessageBox.Show(parent.GetString());
}
private void button6_Click(object sender, EventArgs e)
{
HandleClass6 h = new HandleClass6();
Class7 childObj = new Class7();
Class6 parentPnt = childObj;
MessageBox.Show(parentPnt.GetString()); // virtual
MessageBox.Show(parentPnt.GetStringEx());
////父类变量指向之类的对象，上溯造型
////由父类变量实现的方法调用，如果该方法是虚方法，并且子类中实现override，那么
////调用的实际上就是子类方法。
//Class6 newobj = new Class14();
////reflection
////MEF
//MessageBox.Show(h.GetClass6String(newobj));//?
}