Re: Online activity

Instead of using a basic bit flag, use the userid as the flag. i.e. :

UPDATE table SET lockedByUser =3D <userId> WHERE rowId =3D <editRow> AND
(lockedByUser IS NULL OR lockedByUser=3D<userId>)

Then either read the row data to see if you have the lock, or check how
many rows were affected (0 or 1)

The above technique allows only a single user to pass the check and is
resilient to browser windows closing, session timeouts, etc

The flag will remain indefinitely unless you separately clear flags
(perhaps also include a lockTime so you know which are old and stale),
but will always allow the user that created the lock to re-apply for the
edit mode, and to clear the flag in the usual way (i.e. after hitting
save or cancel)


> -----Original Message-----
> From: Discussion of advanced .NET topics. [mailto:ADVANCED-
> [email protected]] On Behalf Of Paul Cowan
> Sent: 11 October 2009 09:01
> To: [email protected]
> Subject: [ADVANCED-DOTNET] Online activity
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> Hi,
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> I am working on an application where different users will process
> different
> database records off a web page.
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> They will select different records from a grid on a web page and then
> complete the details before saving.
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> My question resolves around how I can stop 2 different users accessing
> the
> same record at the same time.
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> I could have a flag in place that signifies that the record is being
> worked
> on but there are edge cases surrounding this approach.
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> My worry is that a user might start processing a record and then for
> whatever reason just finish the browser session without actually
> finishing
> the record and the flag will remain as being processed.
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> I am sure this is quite a common use case.  Any ideas?
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> Cheers
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> Paul Cowan
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> Cutting-Edge Solutions (Scotland)
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