Detecting user changes on a form....

Question

I have a form with a tab control on it. On each tab page I have lots of checkboxes which represent answers to questions that are presented to the user.

I only want to save what the user has answered and am struggling with a way to iterate through the controls on each tabpage and saving only what the user has answered OR HAS CHANGED, in which I would just update the database instead of "inserting" a record.

Any suggestions on detecting changes?

Thanks in advance...

Daniel · Answer

Alan. Thanks for the great info. I built a protoype yesterday to test different wasy to do it and I will try out your second suggestion. Here's what I did: I created a new property to the checkbox control called HasChanged. On the Load of the form I iterate all the checboxes and wire the CheckStateChanged event to a method i created. The method I created sets that property to TRUE when triggered. That works and is simple but does not account for let's say someone unchecked a checkbox and then deciding to recheck it which should NOT be marked as a change. I need a way to account for a reset to the original state and not mark that as a change. I haven't worked with hashtables before so I'll try to brush up on that concept. Thanks again.

Alan · Answer

The only way I can think of doing this without handling the CheckChanged event is to save the initial 'Checked' state of the CheckBoxes to a HashTable or generic Dictionary field. The key would be the Name property of the CheckBox and the value would be a boolean - true (checked) or false (unchecked). When you're iterating through the CheckBoxes you can then compare the current state of the Checked property with the initial state. If it's changed you can save it to the database and (if the operation may be repeated) update the HashTable or Dictionary with the new value. Alternatively you could handle the CheckChanged event but just save the CheckBox that has changed and its new value to a HashTable or Dictionary. When the Save button is pressed you could then just iterate through the HashTable and save the changes to the database before clearing the HashTable if the operation is to be repeated. Using this second approach if the user changed the same CheckBox twice in the same session so that it reverted to its original state you'd need to remove it from the HashTable so that it wouldn't be saved to the database.

Daniel · Answer

Thanks for the replay. I have considered that but my itention was to process all the checkboxes when the user clicks the save button. Basically when the save is initiated iterate through all the checkboxes find the ones that have been changed and save only those to the database. Hope that makes more sense. Based on that any additional thoughts???

Jan Montano · Answer

I'm not quite sure what you're getting at here but would handling the CheckChanged event of the checkbox be sufficient? This way you'll be sure to process it if the user changed it's value.