Windows 10 Universal App compiled Bindings / x:bind not working

I've got the following code to test out the new Compiled Bindings in Universal Windows 10 Apps.

XAML:

<Page
x:Class="xBindTest.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:xBindTest"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
DataContext="{Binding RelativeSource={RelativeSource Self}}">

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">

        <TextBlock x:Name="Tester" Text="{x:Bind myBindClass.TestText, Mode=OneWay}" ></TextBlock>
        <TextBlock x:Name="Tester2" Text="{Binding myBindClass.TestText, Mode=OneWay}" ></TextBlock>
        <Button x:Name="button" Content="Button" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>

    </StackPanel>            

</Grid>

Code Behind:

Public Class xBindClass : Implements INotifyPropertyChanged

    Private _TestText As String

    Public Property TestText As String
        Get
            Return _TestText
        End Get
        Set(value As String)

            If _TestText <> value Then

                _TestText = value
                NotifyPropertyChanged("TestText")

            End If
        End Set
    End Property

    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Private Sub NotifyPropertyChanged(<CallerMemberName> Optional propertyName As String = "")
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub

End Class

''' <summary>
''' An empty page that can be used on its own or navigated to within a Frame.
''' </summary>
Public NotInheritable Class MainPage
    Inherits Page


    Public Property myBindClass As xBindClass

    Public Sub New()

        ' Add any initialization after the InitializeComponent() call.

        myBindClass = New xBindClass With {.TestText = "Hello"}

        ' This call is required by the designer.
        InitializeComponent()

    End Sub

    Private Sub button_Click(sender As Object, e As RoutedEventArgs) Handles button.Click
        myBindClass.TestText &= " There"

        Tester.DataContext = myBindClass.TestText

    End Sub
End Class

I'm testing the two Binding Types side by side... The Standard {Binding...} type is working fine, but the new x:Bind isn't working strangely...

Perhaps I'm misunderstanding how the new binding works? But I understood, that x:Bind bound to the CodeBehind, and all that was required was a public property to bind to, and you were off and running.

I'm using VS2015 RC and Win 10 build 10130.

Turns out that x:bind isn't implemented in vb.net for VS2015RC.MS have confirmed this will be implemented in the full RTM