List ibanans = Banans as List; ibananas == null ?

[Arjang Assadi]

Given :

interface IBanana {//code ommited}

class Banana : IBanana {//code omitted}

List<IBanana> banans;

List<IBanana> ibanans = banans as  List<IBanana>;

ibananas == null ? why?

Regards

Arjang