Using Interface variables

Question

I\'m still trying to get a better understanding of Interfaces. I know about what they are and how to implement them in classes.

What I don\'t understand is when you

Answer 1

Because this:

public void ReadItemsList(List items);
public void ReadItemsArray(string[] items);

can become this:

public void ReadItems(IEnumerable items);

Edit

Think of it like this:

You have to be able to do this.

rather than:

You have to be this.

Essentially this is a contract between the method and it's callers.