Hi Kevin,

In addition to Bonnie's excellent info, we have to create questionnaires that require iteration of various controls on forms and execution certain methods and/or access certain properties that some but not all controls may have. With controls developed to an interface it's really to use contructs like:

If (MyControl is MyControlInterface1)
{
    MyControl.MyMethod();
    MyControl.MyProp = ...
}

Bill

>I understand that an interface forces a class to use a defined set of properties and methods.
>
>In the code below, why use the interface? This seems to me to limit the programmer
>who inherits from this class by forcing him/her to add code to their class that they
>may not use. Why not just allow the programmer to implement the class any way they want.
>
>Can someone provide a more concrete purpose for an Interface? I'm guessing that I don't
>full understand.
>
>Thanks
>
>
>

>using System;
>using System.Collections.Generic;
>using System.Text;
>
>namespace Interface1
>{
>    interface IMessage
>    {
>        // Send the message. Returns True if success, False otherwise
>        bool Send();
>
>        // The message to send
>        string Message { get; set; }
>
>        // The address to send to
>        string Address { get; set; }
>
>    }
>
>    public class EmailMessage : IMessage
>    {
>        string _address = "";
>        string _message = "";
>
>        public bool Send()
>        {
>            bool bRetVal = false;
>            return bRetVal;
>        }
>
>        public string Message
>        {
>            get
>            {
>                return _message;
>            }
>            set
>            {
>                _message = value;
>            }
>        }
>
>        public string Address
>        {
>            get
>            {
>                return _address;
>            }
>            set
>            {
>                _address = value;
>            }
>        }
>
>    }
>}
>