Inheritance C # ToString

Question

I have a problem (this is my mistake, I just can not understand what I'm doing wrong), where "ToString" does not call the correct method ...

public class ClassA
{
   public override ToString()
   {
      return "Hello, I'm class A.";
   }
}

public class ClassB : ClassA
{
   public override ToString()
   {
       return "Hello, I'm class B.";
   }
}

ClassB myClassB = new ClassB();
List<ClassA> myClassAList = new List<ClassA>();

myClassAList.Add((ClassA) myClassB);
ClassA tempClassA = myClassAList[0];
Console.WriteLine(tempClassA.ToString());

I get "ToString" from "ClassB" and not "ClassA", what am I doing wrong?

Answer 1

You override ToString in ClassB instead of hiding it from the original, which will cause the overridden method to take precedence. What you can do is ...

public class ClassA
{
    public override string ToString()
    {
        return "Hello, I'm class A.";
    }
}

public class ClassB : ClassA
{
    public new string ToString()
    {
        return "Hello, I'm class B.";
    }
}

...

List<ClassA> theList = new List<ClassA>
{
    (ClassA)new ClassB(),
    (ClassA)new ClassB()
};

ClassA a = theList[0];
Console.WriteLine(a.ToString());

// OR... 

Console.WriteLine(new ClassA().ToString());  // I'm Class A
Console.WriteLine(new ClassB().ToString());  // I'm Class B
Console.WriteLine(((ClassA)new ClassB()).ToString()); // I'm Class A

Answer 2

- . ClassB ClassA, ClassB. .ToString() ClassB.ToString(), .

Answer 3

ToString - , , , , .

, , , ClassA ToString.

, . , "tempClassA", ClassB, ClassB, ToString .

Answer 4

You get the right results. You add an instance of ClassB to your list; even if you consider it as ClassA. Therefore, when you call the virtual ToString method, this will result in a call to ClassB ToString; because it is the actual type of object you are working with.