About interfaces and abstract classes

Abstract class and interface, please refer to the difference between the abstract class and interface, I will not say, then when to select the abstract class, and when to select the interface, OK now I have a situation.

Now I define a person's class, for simplicity's sake, I write briefly, as follows:

public abstract class person

{public

abstract float getweight ();

}

Well, now I have another singer, apparently, he is a man, say inherit, as follows:

Public abstract class Singer:person

{public

abstract void singsong ();

}

Now, I have a dancer, obviously, this is also simple, he is also a person, say inheritance, as follows:

Public abstract class Dancer:person

{public

abstract void Dance ();

}

Now everything is fine, there is no problem, but, another person, he said he will sing, and dance, I call this class for Singerdancer, OK, I'm defining a class,

Public abstract class Singerdancer:singer, dancer

But is that right? C # is not allowed to inherit many, this is not permitted to compile, from another level, this obvious violation of the principle of a single responsibility, then there is no abstract class.

Let's take one more example:

Birds can fly, there is no problem, OK, first define a class first, as follows:

Public abstract class Bird

{public

abstract void Fly ();

}