Resizing WPF Prism Regions - wpf

Question

In a WPF Prism app, I have two separate views in two separate regions, say LeftRegion and RightRegion. I would like to be able to drag the edge of LeftRegion (ie. the view in LeftRegion) like a gridsplitter works. Any ideas on how to accomplish this? Thank you.
EDIT: Here is the ShellView.xaml called by bootstrapper.cs that defines the regions.
<Grid >
<Grid.RowDefinitions>
<RowDefinition Height ="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="215"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ContentControl Grid.Column ="0" Height ="500" prism:RegionManager.RegionName="LeftRegion" />
<GridSplitter Grid.Column ="0" Width="5" HorizontalAlignment="Right" VerticalAlignment="Stretch" ResizeBehavior="CurrentAndNext"/>
<ContentControl Grid.Column="1" Height ="400" prism:RegionManager.RegionName="RightRegion" />
</Grid>

Answer 1

Since Prism regions are nothing but UIElements, typically ContentPresenters, you should be able to use a GridSplitter as usual:
<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:WpfApp2"
prism:RegionManager.RegionName="LeftRegion"
mc:Ignorable="d"
Title="MainWindow" Height="300" Width="300">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="50" />
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<ContentControl prism:RegionManager.RegionName="LeftRegion" />
<GridSplitter Grid.Column="1" Width="5" HorizontalAlignment="Stretch" />
<ContentControl Grid.Column="2" prism:RegionManager.RegionName="RightRegion" />
</Grid>
</Window>