Twice Open Color Dialog box?

Question

I have a form with 8 command button, I use AddHandler for Click event for all buttons.

but when I press a button, cmbColor_Click run twice.

Public Sub OpenForm()
    AddHandler cmbColor1.Click, AddressOf cmbColor_Click
    AddHandler cmbColor2.Click, AddressOf cmbColor_Click
    AddHandler cmbColor3.Click, AddressOf cmbColor_Click
    AddHandler cmbColor4.Click, AddressOf cmbColor_Click
    AddHandler cmbColor5.Click, AddressOf cmbColor_Click
    AddHandler cmbColor6.Click, AddressOf cmbColor_Click
    AddHandler cmbColor7.Click, AddressOf cmbColor_Click
    AddHandler cmbColor8.Click, AddressOf cmbColor_Click
End Sub


Private Sub cmbColor_Click(sender As Object, e As EventArgs)
    Dim _color As New ColorDialog
    Dim _button As Button = CType(sender, Button)
    _color.Color = _button.BackColor
    If _color.ShowDialog() = Windows.Forms.DialogResult.OK Then
        _button.BackColor = _color.Color
    End If
End Sub

Answer 1

If the event handler is being called twice for one event then the event handler has been attached to the event twice.

Ideally, you would track down why AddHandler is being used more than once and eliminate the problem.

However, as a quick fix, you can remove the event handler before adding it - it is not an error to try to remove a non-existent event handler.

So...

Friend Sub OpenForm()
    Dim cmbs = {cmbColor1, cmbColor2, cmbColor3, cmbColor4, cmbColor5, cmbColor6, cmbColor7, cmbColor8}
    For Each cmb In cmbs
        RemoveHandler cmb.click, AddressOf cmbColor_Click
        AddHandler cmb.click, AddressOf cmbColor_Click
    Next
End Sub