"Annotations are Easy!"? - Why can't I get a simple Text Annotation on a DateTimeAxis chart then?

As usual the basics of SciChart seem to be eluding me and I can’t get the simplest of features to work (hence the reference to it in the title).

All I want is an annotation in the top left of the screen in which I can dynamically change the text from the code behind – but no matter what I do it just wouldn’t do it. I therefore started a test project to see if I could work out what was going on and have recreated the problem only using XAML.

It would seem the annotation will only appear if the XAxis is defined as a “CategoryDateTimeAxis” AND it’s defined within “SciChartSurface.XAxes” tags. Any other combination and it won’t work.

Anyway – if someone could cast their eye over my test code and explain what’s happening I’d be most grateful.

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:s="http://schemas.abtsoftware.co.uk/scichart" x:Class="AnnotationTest.MainWindow"
    Title="MainWindow" Height="350" Width="525">
<Grid>

    <s:SciChartSurface HorizontalAlignment="Stretch" VerticalAlignment="Stretch" s:ThemeManager.Theme="Chrome">

        <!-- Works - Slimmed down from the "Annotations are easy" example 
        <s:SciChartSurface.XAxes>
             <s:CategoryDateTimeAxis AxisAlignment="Bottom" AxisTitle="XAxis 1" Id="XAxis1" TextFormatting="0.0#" AutoRange="Always"/>
        </s:SciChartSurface.XAxes> 
        -->
        <!-- Doesn't Work and this is from the "Interactions with Annotations" example 
        <s:SciChartSurface.XAxis>
            <s:CategoryDateTimeAxis AutoRange="Always"/>
        </s:SciChartSurface.XAxis>   
        -->

        <!-- Doesn't Work - Slimmed down from the "Create Annotations Dynamically" example
        <s:SciChartSurface.XAxis>
            <s:CategoryDateTimeAxis/>
        </s:SciChartSurface.XAxis>
        -->

        <!-- Doesn't Work - How our Axis are currently defined and what I would like to put a text annotation on
        <s:SciChartSurface.XAxis>
            <s:DateTimeAxis AxisTitle="Date" Id="XAxis1" AxisAlignment="Bottom"></s:DateTimeAxis>
        </s:SciChartSurface.XAxis>
        -->

        <s:SciChartSurface.YAxis>
            <s:NumericAxis TextFormatting="0.0#" VisibleRange="0, 10"/>
        </s:SciChartSurface.YAxis>

        <s:SciChartSurface.Annotations>
            <s:TextAnnotation HorizontalAnchorPoint="Center" Text="Anchor Center (X1, Y1)" VerticalAnchorPoint="Bottom" X1="5.0" XAxisId="XAxis1" Y1="8.0"/>
        </s:SciChartSurface.Annotations>

    </s:SciChartSurface>

</Grid>