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c# - C#从基类访问派生类变量

问题描述

鉴于以下情况：

public class A
{
  public A()
  {
  
  }

}

public class B : A
{
  public int b;
  
  public B()
  {
    
  }
}

public A a = new B();
print(a.b); // I'd like to have many classes that inherit from A, and storing
// one of them on a single variable. Then access the variables that belong to the //derived class

我的目标是创建几个从基类继承的类。然后将其中一个类分配给一个变量（其类型必须是“A”类型）并访问派生类的变量。是否可以？

标签： c#

解决方案

这不是继承的工作方式。

子级可以从父级继承，但父级不能继承或访问仅在子级上的任何内容。

但是您可以测试它是否是子类型，然后显式转换，或者在检查时进行转换。

 A one = new B();
 A two = new A();

 //Check if one is of type B
 if (one.GetType() == typeof(B))
 {
        //Now you can explicitly cast it.
        B newVar = (B)one; 
 }

if (two.GetType() == typeof(B))
{
        //False, will not reach this point
}

//Cast and check at same time to new variable called first
if(one is B first)
{
        //Logic here using first
}

if (two is B second)
{
        /False, will not reach this point
}

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