XAML for window that creates buttons that have a binding for FontSize

MainWindow.xaml

<Window x:Class="Wpf.Binding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Wpf.Binding"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <Style TargetType="Button">
            <Setter Property="FontSize" Value="{Binding FontSizeLabel}" />
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <Button Grid.Row="0" x:Name="AddButton" Click="AddButton_Click">Add Button</Button>
        <Button Grid.Row="1" x:Name="ToggleSizeButton"  Margin="0 5" Click="ToggleSizeButton_Click">Toggle Size Button</Button>
        <ItemsControl Grid.Row="2" x:Name="ButtonList">
            <Button>Existing Button</Button>
        </ItemsControl>
    </Grid>
</Window>