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 <(E-Mail Removed)> wrote:
> 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?

You should throw an ArgumentNullException, as per the documentation.
The normal Hashtable should never pass you a null reference though.

--
Jon Skeet - <(E-Mail Removed)>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

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...

"Jon Skeet [C# MVP]" <(E-Mail Removed)> schrieb im Newsbeitrag
news:(E-Mail Removed)...
> Philipp Schumann <(E-Mail Removed)> wrote:
>> 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?
>
> You should throw an ArgumentNullException, as per the documentation.
> The normal Hashtable should never pass you a null reference though.
>
> --
> Jon Skeet - <(E-Mail Removed)>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too

Philipp Schumann <(E-Mail Removed)> wrote:
> 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...

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.

--
Jon Skeet - <(E-Mail Removed)>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too