Set TextBlock.FontSize for Grid

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="Microsoft.Samples.Graphics.RectangleExample"
    WindowTitle="Sample">
  
  <Canvas>
    <Grid Margin="4" TextBlock.FontSize="20">
        <TextBlock Margin="8" VerticalAlignment="Center">Exclude</TextBlock>
    </Grid>

  </Canvas>
</Page>

