I can't access a derived class method that is instantiated in an array

Question

I was testing with some code and occasionally I can't access a method that is in a derived class.What could I be doing wrong?

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            A[] test = new A[2];
            test[0] = new B();
            test[0].Example();
            test[0].Example1();
        }
        public class A
        {
            public void Example()
            {

            }
        }
        class B : A
        {
            public void Example1()
            {

            }
        }
    }
}

Answer 1

You need to cast it to B type like this:

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            A[] test = new A[2];
            test[0] = new B();
            test[0].Example();
            (test[0] as B).Example1();
        }
        public class A
        {
            public void Example()
            {

            }
        }
        class B : A
        {
            public void Example1()
            {

            }
        }
    }
}

If you want to learn more about casting check the Docs.

Edit: Casting works in this case because test[0] is of type B, if that wasn't the case the expression (test[0] as B) will return null which causes a NullReferenceException and means that test[0] cannot be casted to the type B.