Customizing Hashtable

  • Thread starter Thread starter Philipp Schumann
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Philipp Schumann

Hi,

I use a custom IHashCodeProvider with a Hashtable. What would your take be
on the question what this should return to indicate "invalid" (as for null
references) -- zero?

Thanks,
Phil
 
Philipp Schumann said:
I use a custom IHashCodeProvider with a Hashtable. What would your take be
on the question what this should return to indicate "invalid" (as for null
references) -- zero?
Click to expand...

You should throw an ArgumentNullException, as per the documentation.
The normal Hashtable should never pass you a null reference though.
 
I know---I should have been more clear: what is in the Hashtable are
WeakReferences (I want to prevent the Hashtable from preventing garbage
collections of the objects it is referencing). So I want to return the
GetHashTable of a weakReference.Target, which may be null...
 
Philipp Schumann said:
I know---I should have been more clear: what is in the Hashtable are
WeakReferences (I want to prevent the Hashtable from preventing garbage
collections of the objects it is referencing). So I want to return the
GetHashTable of a weakReference.Target, which may be null...
Click to expand...

So the key itself isn't null, it's just a property of the key which is
null. In that case you could return whatever you want. There's a
difficulty here though - that hashcode function effectively changes
over time. If you put a weak reference in the hashtable as a key, then
if the object the weak reference refers to is garbage collected, you
won't be able to find that key again, because the hashcode you're going
to return has changed.
 
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