Kevin,

By adding the Interface to an already existing class, you'll have to add the three new properties to the class or you'll get the compiler errors. The way to implement the interface it with a comma, as you tried to do:

public class MyTextBox :  System.Windows.Forms.TextBox, IBindingInfo
{
  public string MyPropertyOne, MyPropertyTwo, MyPropertyThree;
}

Simply adding the interface to an already existing class does not automatically add the properties. If you create a new class from scratch, and specify then that it implements an Interface, you'll get some Intellisense that tells you to press TAB and it will fill in the Interfaces properties & methods.

~~Bonnie