[RESOLVED] Change BackColor of empty panels in FlowLayoutPanel

[Clutch001]

Hello All
It's been years since I've programmed VB and it seems I've forgotten more than I remember. I'm just working on a simple calendar (based on someone else's code) and I'm trying to change the BackColor of the empty panels in a FlowLayoutPanel. If there is no label text then the panel would be a different color. It's not really important to the calendar, but it's bugging me that I can't figure it out myself(even though I'm sure it's simple). Thanks in advance.

    Private Sub GenerateDayPanel(ByVal totalDays As Integer)
        flDays.Controls.Clear()
        listFlDay.Clear()
        Dim pflowh As Integer
        pflowh = pnlFlow.Height
        For i As Integer = 1 To totalDays
            Dim fl As New FlowLayoutPanel
            fl.Name = $"flDay{i}"
            fl.Width = Label1.Width
            fl.Height = pflowh / 6
            fl.Margin = New Padding(0)
            fl.BackColor = Color.DimGray
            fl.BorderStyle = BorderStyle.FixedSingle
            fl.Cursor = Cursors.Hand
            fl.AutoScroll = True
            '  AddHandler fl.Click, AddressOf AddNewAppointment
            flDays.Controls.Add(fl)
            listFlDay.Add(fl)
        Next
    End Sub

 Private Sub AddLabelDayToFlDay(ByVal startDayAtFlNumber As Integer, ByVal totalDaysInMonth As Integer)
        For Each fl As FlowLayoutPanel In listFlDay
            fl.Controls.Clear()
            fl.Tag = 0

            fl.BackColor = Color.White

        Next
        Dim myMargin = New Padding
        myMargin.All = 0



        For i As Integer = 1 To totalDaysInMonth
            Dim lbl As New Label
            lbl.Name = $"lblDay{i}"
            lbl.AutoSize = False
            lbl.TextAlign = ContentAlignment.TopLeft
            lbl.Margin = myMargin
            lbl.Text = i
            lbl.Font = New Font("Microsoft Sans Serif", 18)
            listFlDay((i - 1) + (startDayAtFlNumber - 1)).Tag = i
            listFlDay((i - 1) + (startDayAtFlNumber - 1)).Controls.Add(lbl)

            If New Date(currentDate.Year, currentDate.Month, i) = Date.Today Then
                listFlDay((i - 1) + (startDayAtFlNumber - 1)).BackColor = Color.Aqua
            End If

        Next

    End Sub

[jmcilhinney]

I'm trying to change the BackColor of the empty panels in a FlowLayoutPanel. If there is no label text then the panel would be a different color.

So all Panels contain a Label and an "empty" Panel is one where the Text of that Label is an empty String? In that case:

Dim emptyPanels = myFlowLayoutPanel.Controls.
                                    OfType(Of Panel)().
                                    Where(Function(p) p.Controls.
                                                        OfType(Of Label)().
                                                        First().
                                                        Text = String.Empty).
                                    ToArray()
 
For Each p In emptyPanels
    'Do as required.
Next

If you wanted to be able to change the colour both ways:

For Each p In myFlowLayoutPanel.Controls.OfType(Of Panel)()
    If p.Controls.OfType(Of Label)().First().Text = String.Empty Then
        'The Panel is "empty".
    Else
        'The Panel is not "empty".
    End If
Next

Note that, if the FlowLayoutPanel contains only Panel controls then OfType would work but Cast would be more appropriate. As provided, the code will examine the first Label control in each Panel. It could be adjusted to work slightly differently if required.

[Clutch001]

Thanks so much for replying. I kept trying to use your code but just kept getting sequence contains no elements. But it's OK I figured out a quick "cheap" way to do it. I set the initial empty panel back color , and then changed the created label color's back color, and then changed the panels back color .

   For Each fl As FlowLayoutPanel In listFlDay
            fl.Controls.Clear()
            fl.Tag = 0

            fl.BackColor = Color.LightGray

        Next


  lbl.BackColor = Color.White
            If lbl.BackColor = Color.White Then
                listFlDay((i - 1) + (startDayAtFlNumber - 1)).BackColor = Color.White
            End If