问题
Is multiple inheritance possible in VB .Net? If so, what is the syntax?
回答1:
Short answer: No
Slightly longer answer: Yes, if you inherit multiple interfaces, and a single base class. Since this is usually the reason for MI (you want to implement multiple interfaces), it's usually enough. However, in those rare instances where "real" MI is useful, .NET prevents you from doing it.
回答2:
It's possible in a restricted manner in VB.Net in the same way that it is in C#: via Interfaces. Since an interface works out to essentially a pure-abstract base class, you can inherit from as many of those as you need and from one real class.
回答3:
Likely what you want to do is really composition or aggregation ( see here for design pattern). Maybe you're defining a behavior. You can always implement an interface SomeInterface in the base class, have a member of type SomeInterface (which lets it be any class that implements SomeInterface and can hence have the code does the implementing), in the members constructor pass a reference to the base class that owns it if necessary (if doing so, try to add another interface to define the callbacks, the base class will implement it and the subclass will have it as the member variable type). Use calls to the member class to implement SomeInterface. This way the code is implemented in another class, which makes it easy to maintain, but you're not doing multiple inheritance.
The idea behind composition is that an engine is not a car but a car has an engine. The car needs an engine, but doesn't need to know how a whole engine unit works, just how to interface with it. So the engine should not inherit from car. But having the car implement the engine is silly. So the car gets an engine as a member of the whole car, but as an object. The car has an engine as part of its composition.
It sounds like what you are doing is more of a behavior, like a duck object that has a quack behavior, but rubber ducks are ducks but do not quack but squeak. So they differ from mallard objects, but both have many other duck features in common. So you want to have a quack interface that each implements differently. But many ducks will quack for this interface, so you don't want to have to write quack for each one. That's where you use composition to implement the quack behavior interface.
回答4:
As far as I know VB.net does not support multiple inheritance in general but you can reach a kind of multiple inheritance by working with interfaces (using “Implements” instead of “Inherits”):
Public Class ClassName
Implements BaseInterface1, BaseInterface2
End Class
That works fine for classes but I’d like to have an interface inheriting some base interfaces. Something like that:
Public Interface InterfaceName
Implements BaseInterface1, BaseInterface2
End Interface
But the “Implements” keyword is not allowed for interfaces (what makes sense, of course). I tried to use a kind of abstract class which I know from Java:
Public MustInherit Class InterfaceName
Implements BaseInterface1, BaseInterface2
End Class
But now I need to implement the defined methods from BaseInterface1 and BaseInterface2 within the InterfaceName class. But as InterfaceName should be an interface, too, I don’t want to have to implement these methods within that class.
In C# you can do that quite easy:
public interface InterfaceName: BaseInterface1, BaseInterface2 {}
来源：https://stackoverflow.com/questions/351242/is-multiple-inheritance-possible-in-vb-net