C# Foreach döngüsünde tanımlanmamış değişkeni de bulması

<stackpanel x:Name="NavbarStackPanel">
    <stackpanel x:Name="AppearanceStackPanel">
        <button x:Name="Appearance"/>
        <grid x:Name="AppearanceIsActive"/>
    </stackpanel>
    <stackpanel x:Name="LanguageStackPanel">
        <button x:Name="Language"/>
        <grid x:Name="LanguageIsActive"/>
     </stackpanel>
</stackpanel>

        private void NavbarButton_Click(object sender, RoutedEventArgs e)
        {
            string parentName = ((Button)sender).Name;
            foreach (StackPanel stackPanel in NavbarStackPanel.Children)
            {
                foreach (Grid grid in stackPanel.Children)
                {
                    if (grid.Name == parentName + "IsActive")
                    {
                        grid.Visibility = Visibility.Visible;
                    }
                    else
                    {
                        grid.Visibility = Visibility.Collapsed;
                    }
                }
            }
        }

System.InvalidCastException: 'Unable to cast object of type 'Windows.UI.Xaml.Controls.Button' to type 'Windows.UI.Xaml.Controls.Grid'.'

foreach (UIElement element in stackPanel.Children)
                {
                    if (element is Grid grid)
                    {
                        if (grid.Name == parentName + "IsActive")
                        {
                            grid.Visibility = Visibility.Visible;
                        }
                        else
                        {
                            grid.Visibility = Visibility.Collapsed;
                        }
                    }
                }