WrapPanel get First child element when resizing

Question

I have a user control PianoScore and it has WrapPanel in order to display many bars. For example, here is a piano score with 8 bars.

<ScrollViewer VerticalScrollBarVisibility="Auto">
    <WrapPanel Name="WrapPanel_Bars" Orientation="Horizontal" >
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
        <local:BarRenderer></local:BarRenderer>
    </WrapPanel>
</ScrollViewer>

And the thing is, whenever the WrapPanel_Bars gets resized, I need to add a Treble Clef and Bass Clef to every first bar element of the line.

I'm looking for some callback methods for example:

private void WrapPanel_Bars_SizeChanged(object sender, SizeChangedEventArgs e)
{
        var renderers[] = /* How can I get every first BarRenderer of WrapPanel??? */
        foreach (var renderer in renderers)
        {
            // Set renderer's clefs
            renderer.UpClef = Clefs.Treble;
            renderer.DownClef = Clefs.Bass;
        }
}

Expected result:

Sorting BarRenderers by 3

Sorting BarRenderers by 2

I appreciate any kind of your help. Thanks.

Answer 1

Get 'sender as WrapPanel' in the handler method and iterate its Children property while casting each child to BarRenderer.