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MS Access Forum / ActiveX Controls / January 2005cached data in ActiveX control in multi-user environment
I have read/skimmed several Access texts including Balter's Access 2003 and watched many of the AppDev Access tutorials. I probably missed it, but I don't know where this topic is covered. Any suggestions pointing me in the right direction will be greatly appreciated. I am adding a DBI Tech ActiveX control to my Access project (ctMDay calendar control displays scheduled tasks graphically). It does not support data binding. I have implemented the code that copies all the relevant Access table fields (dates, times, task descriptions) to ctMDay, and they display correctly. Looks great. I have not yet implemented the code to copy the information from the control back to the Access table after any edits, but I think I can learn that with a bit more reading. The part I'm grappling with is the multi-user environment. The ActiveX control has a copy of some of the database. Multiple users can change dates, times, tasks, etc using either the ActiveX control and/or database forms. How do I manage this cached information in the ActiveX control so that everyone sees the same schedule information? Is there a small example or tutorial somewhere that illustrates this concept and implementation? Best, Christopher Hi Christopher, as i understand you - following solution can be implemented. in tasks table you can add a new field where your store date/time of record update. on a form with ctMDay at form timer event you check every say 2 mins if any changes occured, if yes - then repopulate ctMDay HTH  SignatureAlex Dybenko (MVP) http://Alex.Dybenko.com http://www.PointLtd.com >I have read/skimmed several Access texts including Balter's Access 2003 and >watched many of the AppDev Access tutorials. I probably missed it, but I [quoted text clipped - 19 lines] > Best, > Christopher Hi Alex, Many thanks for responding. > as i understand you - following solution can be implemented. in tasks > table Yes, the basic info is: tblTasks [TaskID, ScheduleDate, StartTime, StopTime, Description] > you can add a new field where your store date/time of record update. Yes, and this info can be added/edited/deleted via both normal Access forms and Access form with the ActiveX control. > on a form with ctMDay at form timer event you check every say 2 mins if > any changes occured, if yes - then repopulate ctMDay OK, sounds good. I see two form properties "On Timer" and "Timer Interval". So, to make sure the displayed data is accurate, every couple of minutes, I check to see if anything has changed (a table dirty property?) and then redraw the calendar if necessary. Next, about record locks to avoid race conditions. Suppose a user wants to drag a task to a new data/time using the ActiveX control. I think the steps are something like the following. - attempt to lock the record - if the lock fails, then abort the drag-and-drop with a message that the record is locked - if the lock succeeds, then upate the record, then release the lock Am I on the right track? If so, two quick questions. - What is the ADODB code snippet to lock and unlock a record? - The ActiveX control includes many events which I assume are more or less industry standard. At what time do I abort a failed drag-and-drop? Do I let them do the drag-and-drop, and then move it back if unsuccessful, or should I abort the drag-and-drop before it actually begins to move? Best, Christopher Hi Christopher, >> you can add a new field where your store date/time of record update. > OK, sounds good. I see two form properties "On Timer" and "Timer > Interval". So, to make sure the displayed data is accurate, every couple > of minutes, I check to see if anything has changed (a table dirty > property?) and then redraw the calendar if necessary. what i suggest is to save date/time of record update, so getting Max() of this field you will know if any data changed > Next, about record locks to avoid race conditions. Suppose a user wants > to drag a task to a new data/time using the ActiveX control. I think the [quoted text clipped - 6 lines] > > Am I on the right track? If so, two quick questions. yes > - What is the ADODB code snippet to lock and unlock a record? you can open recordset with locked option, see online help for proper constant name > - The ActiveX control includes many events which I assume are more or less > industry standard. At what time do I abort a failed drag-and-drop? Do I > let them do the drag-and-drop, and then move it back if unsuccessful, or > should I abort the drag-and-drop before it actually begins to move? i am not so familiar with ctMDay, but i think it should be Cancel argument in one of D&D events, which you can use SignatureAlex Dybenko (MVP) http://Alex.Dybenko.com http://www.PointLtd.com > what i suggest is to save date/time of record update, so getting Max() of > this field you will know if any data changed Good idea. I was planning to add record-level date/time update info to all my major tables anyway. (It's nice to know that someone modified an Invoice or WorkOrder months after it was created). Is there a modular way to do this, or do I just add a couple lines of code to each "After Update" event of affected forms? > i am not so familiar with ctMDay, but i think it should be Cancel argument > in one of D&D events, which you can use Yes, I see the following Cancel methods. - CancelDrop: Prevents an appointment from being dropped into a new time or column. - CancelSelect: Prevents an appointment from being selected. CancelDrop should do the trick. There are quite a few events associated with the control so now I'll have to read through them and determine which one(s) to trigger on. This one looks promising ... - AppPreDrop: Occurs just before an appointment is either created, or dropped (with the mouse) into a new column or start time. Thanks again for your assistance. This project is starting to look quite nice. Best, Christopher Hi Christopher, > Good idea. I was planning to add record-level date/time update info to > all my major tables anyway. (It's nice to know that someone modified an > Invoice or WorkOrder months after it was created). Is there a modular way > to do this, or do I just add a couple lines of code to each "After Update" > event of affected forms? normally, when you have a bound form to this table you just use beforeupdate event to assign textbox control, bound to "LastUpdated" field to date(): me!LastUpdated=date() HTH SignatureAlex Dybenko (MVP) http://Alex.Dybenko.com http://www.PointLtd.com |
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