I was wanting to know is there anyone that is well versed in C# Interfaces and OOP design. Here is my problem. Say for instance I have a pizza ordering system and I have different menu items that a customer can order. For example, pizzas, drinks, salads, and desserts. I want to just start with this small piece of the problem and thats that we all know that pizzas, drinks and salads come in different sizes but if I could have a method that all of these items share a common interface with then if I had a method that I could pass a type IMenuItem into for example and it was able to return the price of every item regardless of whether it was a pizza, drink, salad, or dessert. Can someone help me with how this method that takes an Interface as a parameter should be approached, maybe a small code example. Thanks for any help offered.