Why predefined interfaces exists in .NET
<p>I know concept of interfaces.. but one thing I couldn't understand that Why so many predefined interfaces are in .NET, like IComparable, IClonable, IFormattable, IDisposable? If just method is declared in these interfaces, then even we can define our own method and perom task. Then what is use of interfaces here?</p>

<p>Here my concept to ask this question is only one that Interface can declare only function signature, but can not define functionality... Then why predefined interfaces? Even in that we have to implement method that interface defines, then why that one not our own method?</p>
