A simple question about object re-initialization

[sowen]

think about we have a private hashtable object (variable)

we initialize the objects in some methods, now we create a cleanup
method, we can either new


1) hash = new HashTable();


or


2) hash.Clear();


is there any difference? on speed and resource allocation


I think for HashTable may be no different; what about a Disposable
object?
Will the first way creates garbage if we don't dispose the existed
object?


Thanks