How to expand combo box on focus event? - vb.net

Question

I want to automatically expand Combo box on focus event.
I have set the Droppeddown = True in gotfocus event, but this has a side effect. When click event gets fired, it expands dropdown and closes immediately. How can I avoid it?
Here is Code:
Private Sub cmbElectLoadPS_gotfocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmbElectLoadPS.GotFocus
cmbElectLoadPS.DroppedDown = True
End Sub

Answer 1

What about check if already DroppedDown ?
Private Sub cmbElectLoadPS_gotfocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmbElectLoadPS.GotFocus
if Not cmbElectLoadPS.DroppedDown Then
cmbElectLoadPS.DroppedDown = True
End If
End Sub
If u need this behavior for all your combo controls is better to create your own implementation
Pulic Class CustomComboBox
Inherits ComboBox
Protected Overrides Sub OnEnter(ByVal e As System.EventArgs)
if Not DroppedDown Then
DroppedDown = True
End If
End Sub
End Class

Answer 2

Oh .. add the same value to ComboBox on Mouseup event..
it would do the trick for u :)
sthing like :
private void comboBox1_Enter(object sender, EventArgs e)
{
comboBox1.DroppedDown = true;
}
private void comboBox1_MouseUp(object sender, MouseEventArgs e)
{
comboBox1.DroppedDown = true;
}
Not your best solution.. but it would do the trick :)

Answer 3

Create a timer called tmrDropDown (you should create a timer for each ComboBox) and leave its default properties.
Add this code:
Private Sub cmbBox_GotFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmbBox.GotFocus
tmrDropDown.Enabled = True
End Sub
And
Private Sub tmrDropDown_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmrDropDown.Tick
cmbBox.DroppedDown = True
tmrDropDown.Enabled = False
End Sub

Answer 4

To implement this features for multiple combobox controls, rather than inheriting the combobox as a new custom control, I'd propose this simple solution:
Private Sub AutoDropDownCombobox_Enter(sender As Object, e As EventArgs) Handles _
cboControl1.Enter, cboControl2.Enter ' register additional events here
If Not CType(sender, ComboBox).DroppedDown Then
CType(sender, ComboBox).DroppedDown = True
End If
End Sub