Sure, it can

A class can only inherit from one class, but it can implement many interfaces
An interface is only a contact to implement some methods and properties

I think the vb syntax would be

Public Class txtBase
    Inherits textbox
   Implements IIOEnable 

End Class

Have a look here http://msdn.microsoft.com/en-us/library/ms973803.aspx under 'Interface Inheritance'

>Sounds promising. Btu if my "txtBase" can "implement" the interface, they can't "inherit" from textbox, can they?
>
>
>>I would define an interface IIOEnable and have your subclassed controls implement that interface
>>
>>then - excuse the syntax - vb and c# mixture
>>

>>foreach ( Control ctrl in Me.Controls )
>>{
>>    IIOEnable ctrl1 = ctrl as IIOEnable ;
>>    if( ctrl1 != null )
>>         ctrl1.ioEnable(value);
>>
>>}
>>

>>
>>
>>

>>

>>>I have subclassed textboxes, panels and buttons. For each of those controls, I wrote an IOEnable method. I would like my (subclassed) form to execute these methods. I came up with something like this, which works, but am wondering if there is not a more generic approach to this, because now, each time I subclass a control I have to kind of "register" it here and in every container.
>>>

>>>For Each ctrl As Control In Me.Controls
>>>     If TypeOf ctrl Is txtBase Then
>>>         Dim ctrl1 As txtBase = ctrl
>>>         ctrl1.ioEnable(value)
>>>     End If
>>>     If TypeOf ctrl Is pnlBase Then
>>>         Dim ctrl1 As pnlBase = ctrl
>>>         ctrl1.ioEnable(value)
>>>     End If
>>>     If TypeOf ctrl Is btnBase Then
>>>         Dim ctrl1 As btnBase = ctrl
>>>         ctrl1.ioEnable(value)
>>>     End If
>>> Next
>>>

>>>
>>>In VFP this looked like this
>>>

>>>for each o in this.Controls
>>>        if !pemstatus(o,'IOEnable',5)
>>>            loop
>>>        endif
>>>        o.IOEnable()
>>>    endif
>>>endfor
>>>