FoxPro Programming
Re: VFP9 Hidden Properties and Subclasses...
07/01/2009
11:48:57 AM
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From:
Rick Strahl
To:
Richard Norris
Attachments:
None

Have you done some coverage testing to see if this code gets hit every time? Maybe it's just a different path through the code that's exposing this bug...

Hidden properties are not visible to child classes so it would make sense that this errors.

Is it maybe because even though you've subclasses, the base class accessing that property (should work) but when code fires in your subclass it would break?

+++ Rick ---

Hi all,

Had a strange one today. A customer of ours placed a support call regarding an error they were recieving relating to the cryptographic functionality the system provides. The error was "Property "HPROVIDERHANDLE" is not found (Error 1734)" which indicates the property HPROVIDERHANDLE for the class did not exist.

After some investigation it appears we subclassed the Foundation Classes _Crypt class to extend its functionality. One of the key properties of this class is HPROVIDERHANDLE but it is a HIDDEN property. Subclasses cannot access or modify HIDDEN properties which explained the error. What doesn't make any sense is why it has only errored this once, as all the other times this code has worked without error. I can only assume that there is some bug in VFP which is preventing an access violation on this property from within this subclass most of the time. Has anyone had any experience with this kind of behaviour before or do you think I'm missing something obvious??

TIA

Richard




Rick Strahl
West Wind Technologies

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