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MS Access Forum / Forms Programming / April 2005Undo doesn't reset unbound controls
I have a scheduling form which has several unbound controls so the user can identify the schedule they want to work with. Due to the "crosstab with extras" nature of the scheduling process, I've resorted to using a temporary table and a Save button (hangs head in shame) that inserts the data back into the (properly normalised, I promise!) permanent tables. I want to give the user the option to change their mind if they change one of the unbound controls to look at a different schedule, without having saved changes back to the permanent tables. My problem is that I cannot make the controls return to their original states, even though I am using Cancel = True and Me!Ctrlname.Undo in the BeforeUpdate event code for each of the controls. The code runs, generates no errors, cancels insofar as the AfterUpdate event doesn't fire, but leaves the control showing its changed value - this is true for two combo boxes and an option group containing only 2 radio buttons. Can anybody tell me why this is so, and how to correct this behaviour? Any assistance or advice (apart from "Don't use a temporary table and unbound controls" - believe me, I tried to avoid it!) gratefully received!  SignatureTop 3 comments you don't want to see in other people's code: 3. 'Causes error - will resolve later 2. 'see <nonexistent reference> 1. 'can't remember what this does!!! Don't know why it does this :-( To resolve the issue, set the controls to Null (Me.Ctrlname=Null) or a zero length string if Null does not work (Me.Ctrlname=""). Regards, Andreas > I have a scheduling form which has several unbound controls so the user can > identify the schedule they want to work with. Due to the "crosstab with [quoted text clipped - 17 lines] > Any assistance or advice (apart from "Don't use a temporary table and > unbound controls" - believe me, I tried to avoid it!) gratefully received! Many thanks for the help, Andreas. Unfortunately the controls may not have been null before they were updated, and since they are unbound, I can't use the OldValue property either. Maybe the two things are related - no OldValue property, so no Undoing back to the original value. Can't see why not though. Anybody from Microsoft reading this? Why is OldValue restricted to bound controls? > Don't know why it does this :-( > To resolve the issue, set the controls to Null (Me.Ctrlname=Null) or a [quoted text clipped - 24 lines] > > Any assistance or advice (apart from "Don't use a temporary table and > > unbound controls" - believe me, I tried to avoid it!) gratefully received! Then you might have to store the "old values" in variables and write these values back to the controls rather than just hardcoding the values. Regards, Andreas > Many thanks for the help, Andreas. > [quoted text clipped - 32 lines] >>>Any assistance or advice (apart from "Don't use a temporary table and >>>unbound controls" - believe me, I tried to avoid it!) gratefully received! Bound controls have underlying buffers for storing original, in process of being edited, and edited data. Unbound controls don't have those buffers. OldValue uses the buffers to know what the original value was. Therefore, OldValue and Undo are not available for unbound controls. If you want to mimic that behavior, use an invisible textbox on the form to hold the original value of the textbox (put value in that textbox during the form's Load event and/or other events as appropriate) so that it can be obtained for putting back in the textbox -- all under your programmatic control. SignatureKen Snell <MS ACCESS MVP> > Many thanks for the help, Andreas. > [quoted text clipped - 46 lines] >> > unbound controls" - believe me, I tried to avoid it!) gratefully >> > received! Thanks for that Ken, As you can see, I came to the same way of coping with this as you suggest, but it's nice to have someone more experienced confirm it as the best way to proceed, and to explain why OldValue doesn't work for unbound controls. > Bound controls have underlying buffers for storing original, in process of > being edited, and edited data. Unbound controls don't have those buffers. [quoted text clipped - 56 lines] > >> > unbound controls" - believe me, I tried to avoid it!) gratefully > >> > received! I have come up with my own alternative, but it seems such an unwieldy workaround that I still hope somebody can save me from it.... :-) The workaround is to have an invisible textbox for each control which stores the current value, and can be used to "reset" the control during the AfterUpdate event if required, or itself be updated to the new current value at the end of the AfterUpdate event. > I have a scheduling form which has several unbound controls so the user can > identify the schedule they want to work with. Due to the "crosstab with [quoted text clipped - 17 lines] > Any assistance or advice (apart from "Don't use a temporary table and > unbound controls" - believe me, I tried to avoid it!) gratefully received! |
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