Good Case For Interfaces

Question

I work at a company where some require justification for the use of an Interface in our code (Visual Studio C# 3.5).

I would like to ask for an Iron Clad reasoning t

Answer 1

I don't understand how its extra overhead.

Interfaces provide flexibility, manageable code, and reusability. Coding to an interface you don't need to worry about the concreted implementation code or logic of the certain class you are using. You just expect a result. Many class have different implementation for the same feature thing (StreamWriter,StringWriter,XmlWriter)..you do not need to worry about how they implement the writing, you just need to call it.