That is essentially how it works. A timestamp column is often used - when
the client updates the DB, it essentially says
UPDATE bleh blah bleh WHERE blah blah AND MyTimestamp = TimeStampOnTheRow
It would then check that 1 row was updated. If not, the timestamp has
changed (i.e. another user updated the row).
This is, in general, how most applications work.
Locking is very bad practice except in a very limited set of circumstances.
On Sun, Nov 21, 2010 at 9:58 PM, Davej <galt...@hotmail.com> wrote:
> I'm not sure I understand optimistic locking. The only way I can see
> it working is if the client can send a message to the DBMS saying "I
> want to update table-row-cell xyz to a new value y if the current
> value is still x otherwise abort and return error."
>
> On Nov 15, 2:55 am, Jamie Fraser <jamie.fra...@gmail.com> wrote:
> > If you are using TableAdapters/DataSets, pretty much all of that is
> handled
> > for you automatically.
> >
> > Concurrency is also handled, depending on the options you specified when
> you
> > created the TableAdapters - optimistic concurrency is generally best for
> > everything as it avoids locking.
> >
> > On Thu, Nov 4, 2010 at 2:49 PM, Davej <galt...@hotmail.com> wrote:
> > > I'm looking for a basic outline of the steps that are usually used in
> > > a multi-user database app. So far I've only played with the single-
> > > user situation, so when I load the form I load the form's datagrid...
> >
> > > Try
> > > Me.TblMy_TableTableAdapter.Fill(Me.My_DBDataSet.tblMy_Table)
> > > Catch ex As Exception
> > > MsgBox("Database Error: " & ex.Message)
> > > End Try
> >
> > > And then when the user exits the form I simply save...
> >
> > > Try
> > > Me.Validate()
> > > Me.TblMy_TableBindingSource.EndEdit()
> > > If Me.My_DBDataSet.HasChanges = True Then
> > > If MsgBox("Post Edits to Remote Database?", MsgBoxStyle.YesNo,
> > > _
> > > "UPDATES PENDING") = MsgBoxResult.Yes Then
> > > Me.TableAdapterManager.UpdateAll(Me.My_DBDataSet) ' update
> > > remote database
> > > End If
> > > End If
> > > Catch ex As Exception
> > > MsgBox("Database Error: " & ex.Message)
> > > End Try
> > > Me.Close()
> >
> > > Now what is the outline of the save operation for a simple non-
> > > cascading multi-user situation? I'm thinking you probably want/need to
> > > identify your updates, inserts and deletes and then go through some
> > > sort of read-lock-write-unlock loops? I have no idea. I have no
> > > exposure to this more complex stuff at all.
> >
> > > Thanks,
> >
> > > Dave
>
