[DotNetDevelopment] Re: Interface, what can you really do ?

[It's time to do something]

Thank you ! I can understand what Interface is, How to define it and
how to implement it in various classes, but I still wonder why we have
to use it? At least in the case that it's used like as polymorphism,
and that's why I wanna know the difference between two ways. In other
words, Please compare them to point out some things such as which is
better ? When using this and when using that ? ...
I still need another answer !
Thank you very much !