Passing a Derived Object as a Reference Parameter

[Bruce]

How can I create a method that will take any object derived from a
base class as a reference parameter?

Something like this:

void DestroyObject(r ef BaseObject obj)
{
obj.Dispose();
obj = null;
}

DestroyObject(r ef derivedObject1) ;
DestroyObject(r ef derivedObject2) ;
DestroyObject(r ef derivedObject3) ;

Where derivedObject1, 2 and 3 are of a class type derived from
BaseObject?

Thanks....

--Bruce