Interface, Polymorphism and type cast

Idea:Use of Interface-polymorphism.
Background:C#-note: p.45-50, MSVC#: Chap. 12, 13

Implement the following Class-diagram:

Use a Console-application, the Dog's Speak method should print out: "Woof", the Cow's: "Muuh" and the Philosopher's: "Hello World".
The Philosopher's Think method should print out: "I think, there for I am".

• Create an ISpeak reference speaker and assign it to a Dog object, invoke the Speak( ) method - what happens?.
• Assign speaker to a Cow object and invoke the Speak( ) method - what happens?.
• Assign speaker to a Philosopher object and invoke the Speak( ) method - what happens?.

Can you create a Cow reference and assign it to a Dog object? - if not - why?

Can you invoke the Philosophers Think( ) method directly using the speaker reference? - if not - why?

• Use Type cast to change the type of speaker from ISpeak to Philosoper and invoke Think( ).