c# - Overhead of implementing an interface

Question

One of my colleagues told me that implementing interfaces introduces overhead. Is this true?

I am not concerned about micro optimizations; I just want to know the deeper details this entails.

Answer 1

couldn't resist and tested it and it looks like almost no overhead.

Participants are:

Interface IFoo    defining a method
class Foo: IFoo   implements IFoo
class Bar         implements the same method as Foo, but no interface involved

so i defined

Foo realfoo = new Foo();
IFoo ifoo = new Foo();
Bar bar =  new Bar();

and called the method, which does 20 string concatenations, 10,000,000 times on each variable.

realfoo:   723 Milliseconds
ifoo:      732 Milliseconds
bar:       728 Milliseconds

If the method does nothing, the actual calls stand out a bit more.

  realfoo: 48 Milliseconds
  ifoo: 62 Milliseconds
  bar: 49 Milliseconds