DataGridView.RowLeave fires before a Form button.MouseClick - vb.net

Question

I can't find anything about this anywhere:
I have a form with a DataGridView and a few Buttons. When a row of the datagridview is selected, and I click a button (on the form), dgv.RowLeave triggers before anything else. It triggers even before Click or MouseClick.
That kind of makes sense, but the problem is that the sender of RowLeave(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs) is the DataGridView, not the button. So it doesn't seem to be possible to know at that point what button was clicked on, because sender and e both refer to the DataGridView, not the Form nor the Buttons.
The Click event is triggered, but only after RowLeave was processed.
So is there any way to know where the user clicked, before RowLeave does other things (in my case, resulting in the Button.Click to be never handled), or then from within RowLeave?
Class MainForm
' The form contains a DataGridView and btnQuit (and other buttons)
Private Sub dgv_RowLeave(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs) Handles dgv.RowLeave
ProgrammaticallyDoRowValidation(dgv.CurrentRow.Index) ' This does validation and more.
' But if btnQuit is clicked, I need to know here, or before RowLeave is
' triggered and NOT do this row validation.
' ...
End Sub
Private Sub Form_Click(sender As Object, e As EventArgs) Handles MyBase.Click
Dim frm As Form
frm = CType(sender, Form)
' Translated from Sach's comment below. Code never reaches this event
'(RowLeave prevents it).
End Sub
Private Sub Quit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnQuit.MouseClick
QuitPgm() ' Contains some more stuff.
' Also never executed, because RowLeave is handled first.
End Sub
End Class

Answer 1

I'm using WinForms here, but the idea is the same.
So Events are attached to Controls. A Button is a Control, so is a DataGridView. Then in the Code Behind you have Event Handlers which are essentially methods tied to Control Events.
So when you attach a Click event to a button, behind-the-scenes, VB.NET creates an Event Handler like so:
private void button1_Click(object sender, EventArgs e)
{
}
Now the sender is an object, but it's actually the DataGrid that is passed there. So contrary to your statement So it doesn't seem to be possible to know at that point what button was clicked on you CAN know if a button was clicked on. If it was, and if you have an event handler attached, it will get called. For example, this will show a MessageBox with the button text:
private void button1_Click(object sender, EventArgs e)
{
var btn = (Button)sender;
MessageBox.Show(btn.Text);
}
So if you want to know if the Form was clicked, attach a Click event handler:
private void Form1_Click(object sender, EventArgs e)
{
var frm = (Form)sender;
MessageBox.Show(frm.Text);
}

Answer 2

I'm not sure how you prevent the button click in your RowLeave event, but I think you should use RowValidating event to validate the DataGridView. Let's say we have a DataGridView with only 1 column and a Button. The validation is the column value must not higher than 100. If we put the validation in the RowValidating event, the validation is triggered after the Leave event but before Validated event. If the validation fails, the subsequence events are not fired.
Public Class Form1
Function ProgrammaticallyDoRowValidation(i As Integer) As Boolean
If Convert.ToInt32(dgv(0, i).Value) > 100 Then
Return False
Else
Return True
End If
End Function
Private Sub dgv_RowValidating(sender As Object, e As DataGridViewCellCancelEventArgs) Handles dgv.RowValidating
If Not ProgrammaticallyDoRowValidation(dgv.CurrentRow.Index) Then
e.Cancel = True
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
MessageBox.Show("Buton clicked")
End Sub
End Class
Try running the code and enter a value higher than 100 in the column. You can't click the button because it fails the validation. But if you set the Button's CausesValidation property to False, the validation won't be triggered.
The order of event according to this link is like this:
When you change the focus by using the keyboard (TAB, SHIFT+TAB, and
so on), by calling the Select or SelectNextControl methods, or by
setting the ContainerControl.ActiveControl property to the current
form, focus events occur in the following order: Enter -> GotFocus ->
Leave -> Validating -> Validated -> LostFocus
When you change the focus by using the mouse or by calling the Focus
method, focus events occur in the following order: Enter -> GotFocus
-> LostFocus -> Leave -> Validating -> Validated

Answer 3

So is there any way to know where the user clicked, before RowLeave
does other things (in my case, resulting in the Button.Click to be
never handled), or then from within RowLeave?
Private Sub dgv_RowLeave(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs) Handles dgv.RowLeave
ProgrammaticallyDoRowValidation(dgv.CurrentRow.Index) ' This does validation and more.
' But if btnQuit is clicked, I need to know here, or before RowLeave is
' triggered and NOT do this row validation.
' ...
End Sub
This is a bit of a kludge solution, but within the DataGridView.RowLeave event, you can check if the ContainerControl.ActiveControl Property to see if the currently active control is the one you want to test for. In this case the ContainerControl is the Form.
Private Sub dgv_RowLeave(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs) Handles dgv.RowLeave
ProgrammaticallyDoRowValidation(dgv.CurrentRow.Index) ' This does validation and more.
' But if btnQuit is clicked, I need to know here, or before RowLeave is
' triggered and NOT do this row validation.
' ...
If Me.ActiveControl Is btnQuit Then
' do something
End If
End Sub