Question

There are two classes. Class B dervied from A.

class A
{  }

class B  : A
{  
    public B()
    {  

    }
    public int Number { get; private set; }
}

This gives me the error ‘unable to cast from A to B’.

void Test()
{
    var a = new A();
    var b = (B)a;     // <== unable to cast.
}

How can I cast the object in variable A to class B?

Thank you.

Answer 1

Your code fails because you don’t have a B.

You could do it if you created a B instead of an A:

A a = new B();
B b = (B)a;

You could think of A as Animal and B as Bear.

You can always say a bear is an animal, but if all you’ve got is an unknown animal you can’t always cast it into a bear. That works only if it actually is a bear.