Combining mouseEvents on label in VB.NET - vb.net

Question

I want to combine MouseEnter with MousePressed on a label.
Public Sub populateGrid()
lblTest.BackColor()
lblTest.BackColor = System.Drawing.Color.Red
gbWorkflow.Controls.Add(lblTest)
For j As Integer = 1 To 40
For i As Integer = 1 To 20
Dim L As New Label
L.Size = New Size(30, 30)
L.Text = "L:" + i.ToString + j.ToString
L.BackColor = Color.AliceBlue
Dim x, y As Integer
Dim loc As Point = gbWorkflow.Location
y = loc.Y * (i * 8) '- (gbWorkflow.Height + L.Size.Height) * i
x = loc.X * (j * 8)
L.Location = New Point(x, y)
gbWorkflow.Controls.Add(L)
AddHandler L.MouseEnter, AddressOf L_Enter
AddHandler L.MouseLeave, AddressOf L_Leave
Next
Next
End Sub
Private Sub L_Enter(ByVal sender As Object, ByVal e As System.EventArgs)
Dim TheLabel As Label = CType(sender, Label)
TheLabel.BackColor = Color.Red
End Sub
My idea was to create a method that triggers on MouseDown and changes the value of a boolean variable. I would then use that variable as a condition to apply the changes to the labels. However, that doesnt seem to work...
How can I achieve this in the best way? Or, at all?
Pseudo-code:
When mouse enter label:
if left mousebutton is pressed then
do stuff with the label
Edit:
It also has to work when the mousebutton is still pressed and the cursor is dragged over several labels. All the labels that the cursor crosses while the left button is pressed should be changed.

Answer 1

The MouseDown event delivers what you are after. Sample code:
Private Sub L_MouseDown(sender As Object, e As System.Windows.Forms.MouseEventArgs)
If (e.Button = Windows.Forms.MouseButtons.Left) Then
'Do stuff
End If
End Sub
Adding the event handler:
AddHandler L.MouseDown, AddressOf L_MouseDown
--- UPDATE
As said, you cannot accomplish directly what you want but there are many alternative ways to deliver an equivalent performance. For example:
Boolean flag indicating whether one of the target labels has been clicked (MouseDown) + MouseEnter performing the modifications only if this flag is true. Sample code:
Private LWasClicked As Boolean = False
Private Sub L_MouseDown(sender As Object, e As System.Windows.Forms.MouseEventArgs)
If (e.Button = Windows.Forms.MouseButtons.Left And Not LWasClicked) Then
LWasClicked = True
End If
End Sub
Private Sub L_MouseEnter(sender As Object, e As System.EventArgs)
If (LWasClicked) Then
'Do stuff
End If
End Sub
With the code above, you can "activate the editing" by just clicking on any label (or on a specific one); once it is activated, you can just pass the mouse over any label and the actions will be performed. You will also have to set an event to de-activate this behaviour (example: new Click/MouseDown). As you can see, this delivers an equivalent performance to what you want and is compatible with how events work.
CLARIFICATION: I think that this (or any other alternative on these lines) delivers an excellent performance. If still you don't want that and prefer to do everything with the mouse-button pressed, you would have to rely on something different (e.g., position of the mouse on the screen, analysis triggered by other means; or even events from different threads). What is clear is that what you aim cannot be accomplished with one-thread events of different controls (a new event cannot be started before the previous one has ended).