I have an application whereby I have the behaviour of 2 groupboxes enable/disable based on the value in a combobox.
This combobox however the behaviour for the group boxes only works when I leave the field by tab or click, not when the text changes.
I have tried using the Leave, TextChanged, Validated Events and everytime I have to actually "Leave" the field for it to perform the enabled/disabled of the groupboxes and their subsequent controls.
I need it so that when they choose 1 of the 3 options it immediately changes and doesn't work when they leave the field but when they choose the correct word.
Any assistance would be great I'm tearing my hair out here.
I think you are looking for the event on your combo boxes
SelectedIndexChanged
To stop the user from leaving an invalid field use the event
Validating
set the e.cancel to True if the validation fails
Related
I'm working on a fairly complex Access Database, trying to build forms with custom buttons for working with records. I'm using list boxes to display and navigate through records and all fields for existing records are disabled unless the user presses an edit button. The problem I'm having is that if I press the Edit or Add New button, enabling all of the fields, and then try to change the selection in a combo box, it does not update on the first try.
If I edit a text box first then the combo boxes work fine.
I've determined that the control's beforeUpdate and afterUpdate events are not firing on the first try but the action triggers the form_Dirty event and then it works as expected. I tried setting Me.Dirty = True with the Edit button and that solved the problem but it causes problems with some of my other code and it seems like an unnecessary workaround if only I understood the actual cause of the problem. It also works as expected if I leave the Combo Box unbound, but I am trying to build a template that doesn't require too much work to build new forms off of and I would rather not go that route.
It must have something to do with some bit of code I'm using because I can start a basic form and the combo boxes work fine.
I've started a basic test form and am adding code from my template form bit by bit until the problem arises, but it's a tedious process. Any help would be appreciated.
What am I missing? Is there some way of getting the Combo Box events to fire before the form is dirty?
UPDATE:
I have templates for a basic form, a form with a single subform, and a form with multiple subs in a tab control.
After some more testing I discovered that this problem does not apply to the basic form which has no subforms. This template uses similar code to the others for new, edit, cancel, save and delete buttons and for preventing accidental changes, preventing Form_unload during an edit and so on. The main difference I can think of off the top of my head is that the templates with subforms use class modules and collections to hold various data and pass it between the main form and subforms. Not sure if or how this might relate to combo box functionality.
I built most of this last winter then got too busy over the summer to work on it. Just now picking it up again and I'm having to re-learn a lot of the details of how my code works.
you can try to use Me.CboName.Requery in your After Update event.
I figured it out. I was calling a procedure with a form refresh in it from the Form_Dirty event and for whatever reason the refresh at exactly the wrong time was causing the combo box Before_Update and After_Update events to be skipped and the combo box value to not change. It was also causing text entered into a textbox to overwrite existing text on the first keystroke.
I am working on a Word template that has 5 text boxes on a user form (frmMain).
I have a validation routine for each text box, that checks if the correct format is used (i.e. date format in one text box, only allowing the use of numeric values in another, preventing all text boxes left empty and so on). One of my text boxes is called txtNumber.
As of now, one of the validation sub routine fires on txtNumber_Exit.
I also have a command button (cmdHelp) on the same user form that, when clicked, fires the sub routine that shows another user form (frmHelp) that contains a help text on how to use this template.
My problem is that when I click this command button (cmdHelp), the validation routine for the text box "txtNumber" fires. Hence I am stuck with a message (written by me) in a msgbox that says "Number can not be blank", and the frmHelp is not showing.
After this, none of my text boxes have the focus, but my cmdHelp button does.
So if I click the cmdHelp button now, the frmHelp is correctly showing.
But this is messing up the workflow, making the visual experience a bit fuzzy for the user, given the fact that the user gets unnecessary info on invalid input in the txtNumber text box, and that the user needs to click twice on the cmdHelp button.
How can I avoid this?
I have searched several forums but did not find answer for checking whether ComboBox is already DroppedDown via VBA code.
I have other code on Form_KeyDown events due to which anytime I press vbKeyDown it moves to next record. I need to check if ComboBox is DroppedDown then don't use other code and instead treat the default functionality of access where vbKeyDown will start scrolling through the items of ComboBox displayed in DropDown.
There is no such property, neither an event for OnDropDown or similar.
If the combobox has focus, you can force a dropdown using the DropDown method, but that's as close you can get.
Is this possible to do or are you only allowed to .focus one textbox on each form? I'm looking to highlight more than one textbox at one time if data is empty.
Only one control can have the focus every time (and thus what you request is not possible). In any case, note that the focus is meant for actions (not for visuals) and that only one control can perform actions every time in the GUI thread (e.g., text written in a TextBox or Button being clicked). On the other hand, you might provoke situations similar-enough to various controls getting the focus simultaneously (e.g., text written in various textboxes, coordinated via TextChanged Events: the actions are not performed simultaneously but the user will not realise about it).
If your intention is just highlighting the given control, you shouldn't rely on the focus. The focused control does get somehow highlighted, although this visual effect is not too relevant and, some times, not even perceptible. The best thing you can do is provoking the highlighting effect "manually". For example: Panel surrounding the TextBox, whose dimensions/visibility are affected; or just simply changing the BackColor property of the TextBox.
I have a ComboBox bound to a table field and I want to validate the selection, since only certain selections are valid depending on context. When in the On Validating Event how can I get the Value before or what it is in the table.field before selection changed?
The WinForms ComboBox control doesn't provide the functionality of being able to intercept a value change and cancel it. You can use the Validating event (or, as you describe, subclass the ComboBox and override OnValidating), but these only allow you to keep the focus on the control. You can't actually "cancel" a value change through the validating events.
There are several third-party (DevExpress, for example) packages that provide ComboBoxes that allow you to inspect both the initial and the new values when the value changes and cancel the change if desired, but the ComboBox provided in System.Windows.Forms does not.