Why prefix C# interface names with an “I”

Question

What is the rationale behind this naming convention?

I don't see any benefit. The extra prefix just pollutes the API.

My thinking is inline with Konrad's response to this related question; the chosen answer of which is mostly what I am asking for here.

Answer 1

Its the complete opposite, the naming convention clearly identifies an interface.

For example if you have:

public class Dog : IPet, IMammal {     .... 

Just from reading it, I can safely assume that IPet and IMammal are probably interfaces.

The .NET CLR allows for single class inheritance. So, if I have a base class..I can only inherit one class from it. Lets change the IPet interface to a base class..our example now becomes

public class Dog : Pet, IMammal {     .... 

I am inheriting from the Pet class and implementing the IMammal interface.

If we did it what you are suggesting and removed the letter "I" we have this:

public class Dog : Pet, Mammal {     .... 

Which one is the class I am inheriting from? Which is the interface I am implementing? It gets confusing right? (FYI..you are supposed to put the base class always first, so you could argue that point...but if you are arguing to remove the letter I from prefixing interface names I doubt you follow that practice as well)

As you can see that naming convention easily tells me a lot about my object without me having to investigate further. I can easily see what I am inheriting vs what I am implementing.