Understanding IOC

[Liagapi]

I've recently read about the Inversion of Control (IOC) principle and I have a few questions I'd like to have answered. I've read that in order to implement the principle of IOC, one must not define a class and pass in concrete objects as its constructor's parameters but one must instead use interfaces as its constructor's parameters. My first question is can I implement IOC by defining a class with virtual classes as its constructor's parameters instead of interfaces. After all the whole reason behind using interfaces is to decouple the class from its dependencies and virtual classes can pretty much do that. My second question is can I use abstract classes as parameters instead of interfaces. Thanks in advance for your reply.