Font Size Resources

   
       

<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:s="clr-namespace:System;assembly=mscorlib">

    <StackPanel.Resources>
        <s:Double x:Key="fontsizeLarge">18</s:Double>
        <s:Double x:Key="fontsizeSmall">14</s:Double>
    </StackPanel.Resources>

    <Button HorizontalAlignment="Center" 
            VerticalAlignment="Center" 
            Margin="24">
        <Button.FontSize>
            <StaticResource ResourceKey="fontsizeLarge" />
        </Button.FontSize>
        Button with large FontSize
    </Button>

    <Button HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Margin="24"
            FontSize="{StaticResource fontsizeSmall}" >
        Button with small FontSize
    </Button>

</StackPanel>