C#获取子类属性值 [英] C# Get subclass attribute value

问题描述

我正在努力做到这一点:

I'm trying to make this:

class A { 
   //attibutes
}

class B : A {
   public int classBAttribute = 5;
   // other attributes and methods
}

我的问题是，如果我有一个A类的实例，如何获得B类的实例或访问他的属性?

My question is this if I have an instance of A class how can i get the instance of the B class or access his attributes?

B b = new B();
Application.Add(b);

//other form
A a = Application.GetA();
B b = getBFromA(a);// ???  Note:  B b = a as B; does't work i tried

推荐答案

您无法做到这一点-通常，没有神奇的方法可以从基础对象创建派生对象.

You cannot do this -- there is no magical way to create derived objects from base objects in general.

要启用这样的方案类，B将需要定义一个接受A自变量的构造函数:

To enable such a scheme class B would need to define a constructor that accepts an A argument:

public B(A a)
{
    // do whatever makes sense to create a B from an A
}

然后您可以将其用作

var b = new B(a);

当然，在这之后a和b将是完全不同的对象；改变一个不会影响另一个.

Of course after this a and b will be completely different objects; changing one will not affect the other.

您还应该正确使用术语以避免混淆:classBAttribute不是字段.

You should also get the terminology right in order to avoid confusion: classBAttribute is not an attribute, it is a field.

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