C#从基类访问派生类的属性 [英] Accessing a property of derived class from the base class in C#

问题描述

在 C# 中，当泛型列表仅包含基类时，访问派生类的属性的最佳方法是什么.

In C#, what is the best way to access a property of the derived class when the generic list contains just the base class.

public class ClassA : BaseClass
{
   public object PropertyA { get; set; }
}

public class ClassB: BaseClass
{
    public object PropertyB { get; set; }
}

public class BaseClass
{
}

public void Main
{
    List<BaseClass> MyList = new List<BaseClass>();
    ClassA a = new ClassA();
    ClassB b = new ClassB();

    MyList.Add(a);
    MyList.Add(b);

    for(int i = 0; i < MyList.Count; i++)
    {
        //I would like to access PropertyA abd PropertyB from the derived classes        
    }
}

推荐答案

当然你可以垂头丧气，像这样:

Certainly you can downcast, like so:

for (int i = 0; i < MyList.Count; i++)
{
    if (MyList[i] is ClassA)
    {
        var a = ((ClassA)MyList[i]).PropertyA;
        // do stuff with a
    }

    if (MyList[i] is ClassB)
    {
        var b = ((ClassB)MyList[i]).PropertyB;
        // do stuff with b
    }
}

... 但是，您应该再看看您要实现的目标.如果您有需要访问 ClassA 和 ClassB 属性的公共代码，那么最好将这些属性的访问权限封装到祖先类中的共享、虚拟属性或方法中.

... However, you should take another look at what you're trying to accomplish. If you have common code that needs to get to properties of ClassA and ClassB, then you may be better off wrapping access to those properties up into a shared, virtual property or method in the ancestor class.

类似于:

public class BaseClass
{
    public virtual void DoStuff() { }
}

public class ClassA : BaseClass
{
    public object PropertyA { get; set; }

    public override void DoStuff() 
    {
        // do stuff with PropertyA 
    }
}

public class ClassB : BaseClass
{
    public object PropertyB { get; set; }

    public override void DoStuff() 
    {
        // do stuff with PropertyB
    }
}

这篇关于C#从基类访问派生类的属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！