C# Parent and Child class - picking the child out of a parent class : <p>Does anyone know, why this underlines(error) Suit (Child class of Stock)in the part that says "stock is Suit"?</p>

<pre><code>//Picking Suit out of the Stock
        public System.Collections.ArrayList Suit()
        {
            System.Collections.ArrayList array = new System.Collections.ArrayList(); //looping through Persons array
            foreach (Stock stock in allStock)//using code snippets
            {
                if (stock is Suit) //if it is a customer, display value, if not, return to the array list
                {
                    array.Add(stock);
                }
            }
            return array;
        }
</code></pre>
