Questions

I’m trying to implement custom annotations using the MVVM pattern. I’ve been using your tutorial as an example (https://www.scichart.com/databinding-annotations-with-mvvm/). Everything works as expected if I manually load some example data to the annotations collection. When I actually try to load the data from our database using async method, the annotations are no longer drawn.

Is this by design or am I doing something wrong? Do you have any suggestions how to load annotations when using async code and MVVM patterns? I haven’t had any problems loading the actual time series on the chart using the same pattern.

I also tried binding the SciChartSurface’s Annotations property to AnnotationCollection and then calling ChartAnnotations.ParentSurface.InvalidateElement(), but the issue still persists.

You can easily reproduce this behavior by adding an async call to the examples’s source code:

private async Task Initialize()
{
    var ds0 = new XyDataSeries<double, double>();
    var someData = new RandomWalkGenerator().GetRandomWalkSeries(200); // RandomWalkGenerator is found in the examples source code

    ds0.Append(someData.XData, someData.YData);

    _chartSeries = new ObservableCollection<IChartSeriesViewModel>();
    _chartSeries.Add(new ChartSeriesViewModel(ds0, new FastLineRenderableSeries()));

    // Now create the labels
    _chartLabels = new List<LabelViewModel>
                       {
                           new LabelViewModel(5, -2.5, "Label0", "Label0 Tooltip!"),
                           new LabelViewModel(20, -2, "Label1", "Label1 Tooltip!"),
                           new LabelViewModel(35, 3, "Label2", "Label2 Tooltip!"),
                           new LabelViewModel(50, 1.5, "Label3", "Label3 Tooltip!"),
                       };

    await Test();

    _chartLabels.Add(new LabelViewModel(65, -0.5, "AFTER ASYNC", "Label4 Tooltip!"));
}

private async Task Test()
{
    await Task.Delay(5000);
}