MainWindow.xaml

<Window x:Class="WpfApp1.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:WpfApp1"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        mc:Ignorable="d" Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <StreamGeometry x:Key="Acorn">
            F1 M 16.6309,18.6563C 17.1309,
      8.15625 29.8809,14.1563 29.8809,
      14.1563C 30.8809,11.1563 34.1308,
      11.4063 34.1308,11.4063C 33.5,12 
      34.6309,13.1563 34.6309,13.1563C 
      32.1309,13.1562 31.1309,14.9062 
      31.1309,14.9062C 41.1309,23.9062
      32.6309,27.9063 32.6309,27.9062C 
      24.6309,24.9063 21.1309,22.1562 
      16.6309,18.6563 Z M 16.6309,19.9063C
      21.6309,24.1563 25.1309,26.1562 
      31.6309,28.6562C 31.6309,28.6562
      26.3809,39.1562 18.3809,36.1563C
      18.3809,36.1563 18,38 16.3809,36.9063C 
      15,36 16.3809,34.9063 16.3809,34.9063C
      16.3809,34.9063 10.1309,30.9062 16.6309,19.9063 Z
        </StreamGeometry>
    </Window.Resources>

    <StackPanel Orientation="Vertical">
        <TextBlock FontSize="16" FontWeight="Medium">Viewbox</TextBlock>
        <TextBlock>A control used to scale single child.</TextBlock>

        <Grid MaxWidth="400" Margin="48">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>
            <TextBlock Grid.Row="0" VerticalAlignment="Center">None</TextBlock>
            <TextBlock Grid.Row="1" VerticalAlignment="Center">Fill</TextBlock>
            <TextBlock Grid.Row="2" VerticalAlignment="Center">Uniform</TextBlock>
            <TextBlock Grid.Row="3" VerticalAlignment="Center">UniformToFill</TextBlock>

            <Viewbox Grid.Row="0" Grid.Column="1" Stretch="None">
                <TextBlock>Hello World!</TextBlock>
            </Viewbox>
            <Viewbox Grid.Row="1" Grid.Column="1" Stretch="Fill">
                <TextBlock>Hello World!</TextBlock>
            </Viewbox>
            <Viewbox Grid.Row="2" Grid.Column="1" Stretch="Uniform">
                <TextBlock>Hello World!</TextBlock>
            </Viewbox>
            <Viewbox Grid.Row="3" Grid.Column="1" Stretch="UniformToFill">
                <TextBlock>Hello World!</TextBlock>
            </Viewbox>

            <Viewbox Grid.Row="0" Grid.Column="2" Stretch="None">
                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
            </Viewbox>
            <Viewbox Grid.Row="1" Grid.Column="2" Stretch="Fill">
                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
            </Viewbox>
            <Viewbox Grid.Row="2" Grid.Column="2" Stretch="Uniform">
                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
            </Viewbox>
            <Viewbox Grid.Row="3" Grid.Column="2" Stretch="UniformToFill">
                <Path Fill="Blue" Data="{StaticResource Acorn}"/>
            </Viewbox>
        </Grid>
    </StackPanel>
</Window>