如何实现元素的 1x1 宽高比？

假设我有某种 LiveCharts 图表。当我调整窗口大小时，我需要窗口的长度和宽度之间的比例为 1x1。

XAML 代码：

 <Grid Background="#f5f5f5">
     <Grid.ColumnDefinitions>
         <ColumnDefinition Width="5" />
         <ColumnDefinition />
         <ColumnDefinition Width="5" />
     </Grid.ColumnDefinitions>
     <Grid.RowDefinitions>
         <RowDefinition Height="5" />
         <RowDefinition />
         <RowDefinition Height="5" />
         <RowDefinition Height="40"/>
         <RowDefinition Height="5" />
     </Grid.RowDefinitions>

     <DockPanel Grid.Row="1" Grid.Column="1" Margin="5" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
         <StackPanel DockPanel.Dock="Top" Orientation="Horizontal">
             <Label Content="Номер сечения:"        Width="120" />
             <Label Content="{Binding SliderValue}" Width="100" />
         </StackPanel>

         <lvc:CartesianChart DockPanel.Dock="Top" DisableAnimations="True" LegendLocation="Top">
              <!-- Здесь какой-то график -->
         </lvc:CartesianChart>

     </DockPanel>

     <DockPanel Grid.Row="3" Grid.Column="1" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
         <StackPanel DockPanel.Dock="Left">
             <Slider Value="{Binding SliderValue, Mode=TwoWay}" Margin="5" SelectionStart="0" Minimum="0" Maximum="299" TickPlacement="BottomRight" TickFrequency="1" IsSnapToTickEnabled="True" IsSelectionRangeEnabled="True" />
         </StackPanel>
     </DockPanel>
 </Grid>