Trying to bind the height/width of a grid to a ViewModel

So I have a grid inside a viewbox. Now the grid scales with the viewbox fine. However, I need to know the height and width of the grid in my ViewModel. However it doesn't seem to ever set the Height to anything?

<Viewbox VerticalAlignment="Top" Margin="5,20,5,0">
             <Border BorderThickness="6" BorderBrush="Black" CornerRadius="2">
 
                 <Grid MinHeight="300" MinWidth="400" Height="{Binding Height, Mode=TwoWay}" Width="{Binding Width, Mode=TwoWay}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Column="0" >
                     <ItemsControl ItemsSource="{Binding Viewers}">
                         <ItemsControl.ItemsPanel>
                             <ItemsPanelTemplate>
                                 <Canvas />
                             </ItemsPanelTemplate>
                              </ItemsControl.ItemsPanel>
                              <ItemsControl.ItemContainerStyle>
                             <Style>
                                 <Setter Property="Canvas.Left" Value="{Binding X}" />
                                 <Setter Property="Canvas.Top" Value="{Binding Y}"/>
                             </Style>
                         </ItemsControl.ItemContainerStyle>
                     </ItemsControl>
                 </Grid>
             </Border>
         </Viewbox>
 

And in my ViewModel:

    private int _height;
     public int Height
     {
         get
         {
             return _height;
         }
 
         set
         {
             _height = value;
             OnPropertyChanged("Height");
         }
     }
 
     private int _width;
     public int Width
     {
         get
         {
             return _width;
         }
 
         set
         {
             _width = value;
             OnPropertyChanged("Width");
         }
     }
 

Any ideas?

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