At last I know what duck typing is..

Now I know what duck typing means “If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck”.

Resources:
Duck test, https://en.wikipedia.org/wiki/Duck_test

Must read book

I have to buy the following book: Framework Design Guidelines :Conventions, Idioms, and Patterns for Reusable .NET Libraries (Microsoft Net Development Series) (Hardcover)