WPF Prism ContentControl not displaying the view...

Hi folks,

I am working on a POC using WPF Prism and have setup the entire project. The only issue i seem to face is that the second view "ContentBView" is loaded in full screen when i have a explicitly defined the column definitions and injecting both Views to occupy 50% of the screen. However for some reasons i only get ContentBView Loaded and ContentAView is hidden. When i comment out the ContentBView then ContentAView loads perfectly.

I know i am doing something very dumb, but cant figure out. I am attaching the shell definitions in xaml.

  xmlns:Infra="clr-namespace:Infrastructure;assembly=Infrastructure"
        Title="Shell">
    <DockPanel>
        <Grid>

            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <Grid x:Name="ToolBarRegion" Grid.Row="0">
                <ContentControl prism:RegionManager.RegionName="{x:Static Infra:RegionNames.ToolBarRegion}" />
            </Grid>
            <Grid x:Name="ContentRegion" Grid.Row="1">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition  />
                        <ColumnDefinition  />
                    </Grid.ColumnDefinitions>
                </Grid>
                <ContentControl Grid.Column="0" prism:RegionManager.RegionName="{x:Static Infra:RegionNames.ContentRegionA}"  />
                <ContentControl Grid.Column="1" prism:RegionManager.RegionName="{x:Static Infra:RegionNames.ContentRegionB}"  />
            </Grid>
            <Grid x:Name="StatusBarRegion" Grid.Row="2">
                <ContentControl prism:RegionManager.RegionName="{x:Static Infra:RegionNames.StatusBarRegion}"  />
            </Grid>
        </Grid>
    </DockPanel>
</Window>