What is the difference between an abstract class and an interface?

Question

Possible duplicate:
Interface versus abstract class (generic OO)

Can I create an instance of the Abstract class? If so, why am I not going to abstract all of my unsealed classes?

If I can’t create it, then what is the difference from the interface? Can an abstract class have a “base” class? Is there a difference in the difference between an interface and an abstract class?

Answer 1

You cannot instantiate an abstract class.

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Answer 2

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Answer 3

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abstract class A 
{
    public int Foo() { return 1; } // implementation defined
}

class B : A 
{
}

interface C
{
    int Foo() {return 1;} // not legal, cannot provide implementation in interface
}

// ... somewhere else in code

A a = new A(); // not legal
A a = new B(); // legal

Answer 4

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Answer 5

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Answer 6

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