How do I in visual basic access controls I have created in a programatically created form

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After 47 years as an IT consultant and written code in a number of programming languages I retired 5 years ago and to keep my brain active I converted a program I originally wrote in dBaseIII (yes I am ancient) and migrated through Foxpro into Visual Foxpro (which all are no longer supported by Microsoft) into Visual Basic. I found Visual C# was one step to far for me as my main recent experience was designing large to very large Microsoft Exchange solutions.

I got my programming going but it was rooted into historical forms design. So I decided to have a go at using menus instead. I have the basic redesign going but I need to create a multiple of sub forms programtically otherwise I am going to have a vast number of forms being designed when they are simple enough to be programatically be created and destroyed as required.

My issue concerns accessing the controls I have created on the programatically created form and the events triggered for that form. This is a precis of what I have designed and coded so far:

For my parent form at the Public Class level I declared

Dim frmAuthorEdit As New System.Windows.Forms.Form

I have then placed a databound datagrid on the parent form. When I right click on a grid entry on this form, I enter a sub called gridname.CellMouseDown. Within this sub I create a new form programatically thus

frmAuthorEdit = New Form

and I added an event handler to it like this

AddHandler frmAuthorEdit.Load, AddressOf frmAuthorEdit_Load

I then show the form.

Still within this same parent class I have declared a sub like this

Private Sub frmAuthorEdit_Load(sender As System.Object, e As System.EventArgs)

Within this sub frmAuthorEdit_Load I programatically add to this new form numerous labels, textboxes and command buttons. For example for a new textbox I did

Dim txtDisplayName = New TextBox

and I added an event handler to it thus

AddHandler txtDisplayName.TextChanged, AddressOf txtDisplayName_TextChanged

This all works OK.

Within the sub txtDisplayName_TextChanged I want to be able to access all of the textboxes I have created in the frmAuthorEdit_Load sub when I change information on the frmAuthorEdit form.

As a totally self taught programmer (to aid me with customer projects) object orientated languages are a challenge to me so I apologise for my ignorance in advance in what could be a simple answer.

What I have tried:

VB2019

I have tried changing the declaration Dim frmAuthorEdit As New System.Windows.Forms.Form from the top class level to the frmAuthorEdit_Load sub but neither of these actions solved my problem.

In the sub

Private Sub txtDisplayName_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)

via sender I can extract the text from the textbox selected but my issue is how do I then update other textboxes on this form with the revised text that has changed from the first textbox that kicked off the event?

I have tried everything I can think off and can find under Google but so far I have totally failed. Things I have tried include

frmAuthorEdit.txtDisplayName.text = "New text"

This fails with txtDisplayName is not a member of 'Form'

If I change the command to

me.txtDisplayName.text = "New text"

This fails with txtDisplayName is not a member of 'MyStartFromName' - as I would expect as this control is not on that form.

So how do I access the controls on this programatically created form?

Posted 5-Apr-21 3:12am

Derek Carpenter 2021

Updated 5-Apr-21 3:25am

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OriginalGriff · Accepted Answer · 2021-04-05T03:25:00

If you create them dynamically, then you can't refer to them by name as part of your form - they would each need a separate form level variable for that to work.

But ... assuming that you added each dynamic control to your Form.Controls collection (or a subcontainer) so they are displayed, then you can traverse the relevant collection and find all the controls you added.
And to locate the one that caused the TextChanged event to be raised (he one the user edited) is simple: it's passed to the event handler as the sender parameter.
So all you need to do is cast sender to a TextBox, get the Text from that, and loop though the Controls collection updating all the other controls (remembering to skip the original one).

The only other problem you will have is that each time you update another text box, it will raise it's own TextChanged event - which will not be handled until you exit from the original one, so you will need to skip those events as well. One way to do that is to set the Control.Tag property to indicate that the event should be ignored and just clear it when the event fires - again, the sender property will contain the actual control.