Is there a way to use subclass properties when you only have the baseclass?

Question

So this is what i'm trying to achieve, is there an elegant way to do this?

public class item
{
}

public class A : item
{
   public int a;
}

public class B : item
{
   public string b;
}

public class example
{
  A classA = new A();
  B classB = new B();

  item[] itemArray = {classA, classB}

  foreach(item i in itemArray)
  {
    // get int a if item i is ofType A
    // get string b if item i is ofType B 
  }
}

I've tried overriding but that forces me to create virtual fields of both a and b in the base class. There has to be a better way.

Declare your ints public, then you can do `if (item is A itemA) { Console.WriteLine(itemA.a); } else if (item is B itemB) { Console.WriteLine(itemB.b); }` or by using a switch-case: `switch (item) { case A itemA: …; break; case B itemB: …; break; }`. Also it’s best practice to use properties instead of fields if they are public for a variety of reasons. — ckuri, Dec 11 '20 at 21:28

score 0 · Answer 1 · answered Dec 12 '20 at 23:24

This would probably be the best way, I feel so silly for not thinking about simply casting it to the right class.

public class example
{
  A classA = new A();
  B classB = new B();

  item[] itemArray = {classA, classB}

  foreach(item i in itemArray)
  {
    if(i.GetType() == Type.GetType("A"))
    {
        A blabla = (A)i;
        Console.WriteLine(blabla.a);
    }
  }
}

score -1 · Answer 2 · answered Dec 14 '20 at 23:19

Here's how this should be done:

void Main()
{
    A classA = new A() { a = 42 };
    B classB = new B() { b = "Foo" };

    Item[] itemArray = new Item[] { classA, classB };

    foreach (Item i in itemArray)
    {
        if (i is A i_as_A)
        {
            Console.WriteLine(i_as_A.a);
        }
        if (i is B i_as_B)
        {
            Console.WriteLine(i_as_B.b);
        }
    }
}

public class Item { }

public class A : Item
{
    public int a;
}

public class B : Item
{
    public string b;
}

If I run that I get:

42
Foo

Is there a way to use subclass properties when you only have the baseclass?

2 Answers2