Tag: MVVM

Hi,

Could you provide some Mvvm examples that include:

1) Mvvm bubble chart where the Fill color is defined on the series view model
2) custom tooltips per point where the tooltip string is defined on the point view model

I have both of these kind of working using a workaround based on the obsolete SciChartSurface.SeriesSource property, but now I’m trying to migrate to SciChartSurface.RenderableSeries and the proper Mvvm API and I cannot find all the elements I need.

Cheers
Felix

Hi,

I am developing an MVVM WPF application and need to access the SelectedPointMarkers property of DataPointSelectionModifier from the ViewModel.

From looking at the DataPointSelectionModifier documentation (https://www.scichart.com/documentation/win/current/webframe.html#DataPoint%20Selection.html) I can see how you can get the X and Y coordinate values of a selected point in a view, by binding the PointMarkersSelectionModifier to a listbox.

However this doesn’t really help me, I need to get the coordinates of the SelectedPointMarker into a property inside the ViewModel that can be accessed, rather than just binding to a listbox in the view itself.

I’ve also looked at this similar post: (https://www.scichart.com/questions/wpf/i-want-to-bind-selectedpointmarkers-of-datapointselectionmodifier), but I had no luck getting Kenishis solution to work in my case.

How can i do this?

Thanks.

Hello support team,

We are currently starting a complete redesign of our SciChart implementation from V3.x to V5.x. In V5.x the MVVM pattern is now supported and we would like to use this.
Our main focus is on the performance of the SciChart component. Now the question arises whether the use of the MVVM API is questionable for exactly this reason (performance).
Does it make a big difference whether I address the series directly or via the MVVM API?
Thank you very much for your support!

I’m trying to build a chart control that adheres to MVVM and noticed that I have the option to use NumericAxis or NumericAxisForMvvm, but I’m not sure exactly what the differences would be. I couldn’t really find anything in depth on them in the documentation but maybe I missed something.

Is anyone aware of any differences? I’m assuming NumericAxisForMvvm would be best for what I’m wanting but I’m not exactly sure why.

Thanks!

Hi SciChart team,

I have built a xyscatter chart with DateTime type X-Axis and Double type Y-Axis,
and built boxannotations to mark areas.

May I set the x-Axis value in the tooltip?
Or can I show properties of each item which means every point in the xyscatterseries, and customize the tooltip content style like adding the description of every properties.

Hi
I’m trying to use AvaloniaUI with .NET Core 3.1 to create an application using SciChart, but I get XAMLIL error when trying to add a SciChartSurface following the code from the tutorial. I used a standard Avalonia MVVM Application template when creating the project.

This is the code:

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:s="http://schemas.abtsoftware.co.uk/scichart"
             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"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:Class="FF_DataVis_Avalonia_MVVM.Views.TabControlView">

    <Grid>
        <!-- Bind to ChartViewModel.ChartTitle etc -->
        <s:SciChartSurface ChartTitle="{Binding ChartTitle}">
            <s:SciChartSurface.XAxis>
                <s:NumericAxis AxisTitle="{Binding XAxisTitle}"/>
            </s:SciChartSurface.XAxis>
            <s:SciChartSurface.YAxis>
                <s:NumericAxis AxisTitle="{Binding YAxisTitle}"/>
            </s:SciChartSurface.YAxis>
        </s:SciChartSurface>
    </Grid>
</UserControl>

And the error I get is:
“XAMLIL: Unable to resolve type SciChartSurface from namespace http://schemas.abtsoftware.co.uk/scichart Line 27, position 4″
which is the first s:SciChartSurface entry.

Any ideas what might be wrong? Does SciChart not work with any framework regardless of using .NET Core 3.0?
I have tried changing between Core 3.0 and 3.1, which does nothing.

Hello,

how can i implement a vertically stacked y axis chart like in your example (WPF Chart Vertically Stacked YAxis) with MVVM and a varying number of y axes. Your example has a fixed number of y axes and the needed YAxesPanel is directly implemented in your xaml code. What is the best way to achieve the same result with a varying number of y axis?

Best regards
Alexander

We’re using ReactiveUI and bindings in code-behind. We’re now upgrading from SciChart v3 to v6 and we’re wondering how to use the SeriesBinding in code-behind like this:

public partial class BarChartView : ReactiveUserControl<sBarChartViewModel>
{
    public BarChartView()
    {
        InitializeComponent();

        this.WhenActivated(disposable =>
        {
            this.OneWayBind(ViewModel,
                            vm => vm.SeriesSource,
                            view => view.BarChart.SeriesSource)
                .DisposeWith(disposable);

            this.OneWayBind(ViewModel,
                            vm => vm.LabelProvider,
                            view => view.FaciesAxis.LabelProvider)
                .DisposeWith(disposable);

            this.OneWayBind(ViewModel,
                            vm => vm.TooltipDataContext,
                            view => view.TooltipModifier.TooltipLabelDataContextSelector)
                .DisposeWith(disposable);

            this.OneWayBind(ViewModel,
                            vm => vm.XAxisRange,
                            view => view.FaciesAxis.VisibleRange)
                .DisposeWith(disposable);
        });
    }
}

Now the IChartSeriesViewModel and SciChartSurface.SeriesSource is deprecated so we have to move to IRenderableSeriesViewModel instead and then bind to SciChartSurface.RenderableSeries. But how can we convert from IRenderableSeriesViewModel to IRenderableSeries here?

Getting an exception when trying to add tooltip template MVVM style to a blox plot. The chart also contains a scatter plot which should not be styled. That works fine, hoverwer, when I move the mouse over a box in the box plot, the exception is thrown.

I want to keep the styling, I just want to write something different than the default text.

The template:

  <DataTemplate DataType="scalarPlot:ToolTipData" x:Key="BoxSeriesTooltipTemplate">
    <TextBlock>
      <Run Text="Max:      " />
      <Run Text="{Binding Maximum}" />
      <LineBreak />
      <Run Text="P90:       " />
      <Run Text="{Binding P90}" />
      <LineBreak />
      <Run Text="Median: " />
      <Run Text="{Binding Median}" />
      <LineBreak />
      <Run Text="P10:       " />
      <Run Text="{Binding P10}" />
      <LineBreak />
      <Run Text="Min:       " />
      <Run Text="{Binding Minimum}" />
      <LineBreak />
    </TextBlock>
  </DataTemplate>

The binding:

      <Style TargetType="s:BaseRenderableSeries" x:Key="BoxSeriesStyle">
        <Setter Property="s:TooltipModifier.TooltipTemplate" Value="{StaticResource BoxSeriesTooltipTemplate}"/>
        <Setter Property="s:TooltipModifier.IncludeSeries" Value="True"/>
      </Style>

The modifier:

<s:SciChartSurface.ChartModifier>
      <s:ModifierGroup>
        <s:TooltipModifier IsEnabled="True" ShowTooltipOn="Always" ReceiveHandledEvents="True" TooltipLabelDataContextSelector="{Binding ToolTipDataContext}"/>
      </s:ModifierGroup>
    </s:SciChartSurface.ChartModifier>

The view model:

    private static IRenderableSeriesViewModel CreateBoxPlotViewModel(BoxPlotDataSeries<int, float> boxPlotDataSeries)
    {
        return new BoxPlotRenderableSeriesViewModel
        {
            DataSeries = boxPlotDataSeries,
            Stroke = Colors.SteelBlue,
            Fill = new LinearGradientBrush(Colors.White, Colors.LightSteelBlue, new System.Windows.Point(0, 0), new System.Windows.Point(0.5, 1)),
            StyleKey = "BoxSeriesStyle"
        };
    }

The data context selector:

    public Func<SeriesInfo, object> ToolTipDataContext
    {
        get
        {
            return seriesInfo =>
                   {
                       return seriesInfo switch
                       {
                           BoxPlotSeriesInfo boxInfo =>
                               new ToolTipData
                               {
                                   Fill = seriesInfo.Fill,
                                   Stroke = seriesInfo.Stroke,
                                   Maximum = (float) boxInfo.MaximumValue,
                                   P90 = (float) boxInfo.UpperQuartileValue,
                                   Median = (float) boxInfo.MedianValue,
                                   P10 = (float) boxInfo.LowerQuartileValue,
                                   Minimum = (float) boxInfo.MinimumValue
                               },
                           _ => seriesInfo
                       };
                   };
        }
    }

Hello.
Thanks for previous answer but I can’t check how it work because of new problem. I develop WPF application and try to use MVVM as architecture pattern. In the Model part of my application I used a loop started in the new thread. In that loop I get some data which received to ViewModel and used as chart data. Looks as usual.
But then I tried to set visible range updated object which bound to axis I get exception ‘System.InvalidOperationException: ‘The calling thread cannot access this object because a different thread owns it.’ in my loop. I know it happens in WPF applications and need to use Dispatcher to solve it. But as I know if you try to use MVVM you not needed to use Dispatcher often because WPF-binding in most cases is thread-safe. That happend in my case? How to solve it?
Parts of my code:

XAML

<Window x:Class="HMI.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:s="http://schemas.abtsoftware.co.uk/scichart"
        xmlns:localVM="clr-namespace:MyCom.HMI.ViewModel"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.DataContext>
        <localVM:HMIViewModel/>
    </Window.DataContext>
    <Window.Resources>
        <localVM:InverseBooleanConverter x:Key="InverseBooleanConverter"/>
        <localVM:ProcessStateToColorConverter x:Key="ProcessStateToColorConverter"/>
        <localVM:ProcessStateToStartedConverter x:Key="ProcessStateToStartedConverter"/>
        <localVM:ProcessStateToStoppedConverter x:Key="ProcessStateToStoppedConverter"/>
    </Window.Resources>
    <DockPanel>
        <StackPanel DockPanel.Dock="Top" Orientation="Horizontal">
            <StackPanel DockPanel.Dock="Left" Orientation="Vertical" Width="520">
                <Border DockPanel.Dock="Top" Margin="5" Padding="5" BorderBrush="Black" BorderThickness="1,1,1,1" CornerRadius="5">
                    <StackPanel DockPanel.Dock="left" Orientation="Horizontal" Height="40">
                        <Ellipse Margin="5" Height="20" Width="20" HorizontalAlignment="Left" VerticalAlignment="Center" Stroke="Black" Fill="{Binding ProcessState, Converter={StaticResource ProcessStateToColorConverter}}"/>
                        <Label Content="State" Margin="5" Width="90" HorizontalContentAlignment="Left" VerticalContentAlignment="Center"/>
                    </StackPanel>
                </Border>
                <Border DockPanel.Dock="Top" Margin="5" Padding="5" BorderBrush="Black" BorderThickness="1,1,1,1" CornerRadius="5">
                    <Grid DockPanel.Dock="Left" Height="300">
                        <s:SciChartSurface ChartTitle="Profil" RenderableSeries="{s:SeriesBinding RenderableSeries}">
                            <s:SciChartSurface.XAxis>
                                <s:NumericAxis AxisTitle="Position, m" VisibleRange="{Binding XVisibleRange, Mode=TwoWay}"/>
                            </s:SciChartSurface.XAxis>
                            <s:SciChartSurface.YAxis>
                                <s:NumericAxis AxisTitle="Size, um" VisibleRange="{Binding YVisibleRange, Mode=TwoWay}"/>
                            </s:SciChartSurface.YAxis>
                        </s:SciChartSurface>
                    </Grid>
                </Border>
            </StackPanel>
...

ViewModel

namespace MyCom.HMI.ViewModel
{
    public class HMIViewModel : BindableBase
    {      
        private readonly HMIModel _model = new();

        public HMIViewModel()
        {
            _renderableSeries = new ObservableCollection<IRenderableSeriesViewModel>();

            ((INotifyCollectionChanged)_model.TestControlData).CollectionChanged += (s, e) =>  { TestControlDataChanged(e); };

            InitCharts();
        }

...

        private ObservableCollection<IRenderableSeriesViewModel> _renderableSeries;
        public ObservableCollection<IRenderableSeriesViewModel> RenderableSeries
        {
            get { return _renderableSeries; }
            set
            {
                SetProperty(ref _renderableSeries, value, nameof(RenderableSeries));
            }
        }

        private IRange _xVisibleRange;
        public IRange XVisibleRange
        {
            get => _xVisibleRange;
            set
            {
                if (_xVisibleRange != value)
                {
                    SetProperty(ref _xVisibleRange, value, nameof(XVisibleRange));
                }
            }
        }

        private IRange _yVisibleRange;
        public IRange YVisibleRange
        {
            get => _yVisibleRange;
            set
            {
                if (_yVisibleRange != value)
                {
                    SetProperty(ref _yVisibleRange, value, nameof(YVisibleRange));
                }
            }
        }

        private XyDataSeries<double, double> _lineDataDiameter1;

...

        private void InitCharts()
        { // TODO
            _lineDataDiameter1 = new XyDataSeries<double, double>()
            { 
                SeriesName = "Diameter1"
            };

            RenderableSeries.Add(new LineRenderableSeriesViewModel()
            {
                StrokeThickness = 2,
                Stroke = Colors.SteelBlue,
                DataSeries = _lineDataDiameter1,
                StyleKey = "LineSeriesStyle"
            });
        }

        private void TestControlDataChanged(NotifyCollectionChangedEventArgs args)
        {
            if (args.Action == NotifyCollectionChangedAction.Add && args.NewItems?.Count > 0)
            {
                var testControlActualState = args.NewItems.Cast<TestControlActualState>();

                List<double> xValues = new();
                List<double> yValuesDiameter1 = new();

                foreach (var item in testControlActualState) 
                {
                    if (item.Diameter1 > 0f)
                    {
                        xValues.Add(item.FiberLength);
                        yValuesDiameter1.Add(item.Diameter1);
                    }
                }

                _lineDataDiameter1.Append(xValues, yValuesDiameter1);

                // TODO
                if (xValues.Count > 0)
                {
                    var cuurMaxValueX = xValues.Max();
                    XVisibleRange.Max = cuurMaxValueX;
                    XVisibleRange.Min = cuurMaxValueX - 7000f > 0 ? cuurMaxValueX - 7000f : 0;
                }

                // TODO
                if (yValuesDiameter1.Count > 0)
                {
                    var cuurMaxValueY = yValuesDiameter1.Max();
                    YVisibleRange.Max = cuurMaxValueY + 50;
                    YVisibleRange.Min = 0;
                }
            }
        }

Model

namespace MyCom.HMI.Model
{
    public class HMIModel : BindableBase, IDisposable
    {
        private readonly ObservableCollection<TestControlActualState> _testControlData;
        internal ReadOnlyObservableCollection<TestControlActualState> TestControlData { get; }

        public HMIModel()
        {
            _testControlData = new ObservableCollection<TestControlActualState>();
            TestControlData = new ReadOnlyObservableCollection<TestControlActualState>(_testControlData);
        }

...

        private void StartPollerThread()
        {
            _pollerCancellationToken ??= new CancellationTokenSource();

            if (!_pollerCancellationToken.IsCancellationRequested)
            {
                Task.Factory.StartNew(() => PollerDoWork(_pollerCancellationToken.Token), TaskCreationOptions.LongRunning);
            }
        }

        private void PollerDoWork(CancellationToken cancellationToken)
        {
            try
            {
                Thread.CurrentThread.Priority = ThreadPriority.Lowest;
                IsPollerStarted = true;

                while (!cancellationToken.IsCancellationRequested && (_isKeepConnection || _countOfTrying <= MAX_COUNT_OF_TRYING))
                {
                    try
                    {
                        _testControlData.Add(_emulator.GetTestControlActualState());

                        if (!_isKeepConnection && _countOfTrying > 0)
                        {
                            Thread.Sleep(_pollerTimeout / REASK_COEFICIENT);
                            continue;
                        }
                    }
                    catch
                    {
                        // Thread must be alive!!! ...ALWAYS!!!
                    }
                    Thread.Sleep(_pollerTimeout);
                }
            }
            finally
            {
                IsPollerStarted = false;
                _pollerCancellationToken = null;
            }
        }

Hi sir,

We would like to build a real time updated stackedcolumn chart in mvvm mode.
Is that possible? (x-axis on the left side)(y-axis on the bottom side which can keep update with only 10mins range)

I wonder can I use the StackedColumnRenderableSeriesForMvvm?
I found out this control but have no idea how to use it…

Hi,

I’m trying to evaluate the reality of creating multiple realtime charts and I’m hitting a huge performance brick wall.

My application will have high speed streamed data coming in over ethernet. Currently I’m simulating this with a thread timer that updates 100 data objects at 60Hz. Screen data and chart updates I’ve got throttled to 30Hz but it’s still grinding my charts are still struggling. If I move the mouse pointer the charts freeze entirely until the mouse is still.

I want the end user to be able to choose any data object and chart it however they want. Adding charts and adding plots to charts etc. To enable this I’ve created a chart template as a user control and at runtime the charts are added to a panel on a tab control. Event one chart on one tab chugs though. Move the mouse over it and it locks up.

I have a single overview chart with a scrollbar over the top on the parent control. I need this to control the cursor (vertical line) and shared X visible range. Live data is Fifo limited to a 10 second range. All this works, just painfully slowly.

SharedXVisible range is MVVM bound. Renderable series is LineRenderableSeriesViewModel and data is pushed at 30Hz from a Data provider as per this tutorial:
https://www.scichart.com/documentation/win/current/Tutorial%2006b%20-%20Adding%20Realtime%20Updates%20with%20MVVM.html

CPU usage is sub 20%. Max frame rate is 30fps. Render priority doesn’t seem to make much difference, though “immediate” will lock up the whole app. I’m no expert at performance profiling but I’m not getting any clues from ReShaper dotTrace so far.

I tried creating a version that hand almost no binding and used codebehind to update the data. It didn’t seem to help. I’d rather not do this though as I have a lot of things working that I like such as vertical slice, annotations, templates etc.

I’ve got a list of all the live data on the right of the screen and it all updates rapidly, even while the mouse is moving and the charts are frozen.

I’m also using some Syncfusion controls and theming, if it matters.

I must be missing something obvious surely.

<!--  Define Chart  -->
        <s:SciChartSurface x:Name="chart" Grid.Row="0" Grid.Column="0"
                           Background="Black"
                           RenderPriority="low"
                           MaxFrameRate="30"
                           RenderableSeries="{s:SeriesBinding RenderableSeriesCollection}"
                           >

            <!--  Define X and Y Axis  -->
            <s:SciChartSurface.YAxis>
                <s:NumericAxis AutoRange="{Binding AxisYRangeMode}" 
                               DrawMajorBands="False" 
                               DrawMinorGridLines="false" 
                               DrawMajorGridLines="True" 
                               DrawMajorTicks="False" 
                               DrawMinorTicks="False" 
                               VisibleRange="{Binding AxisYVisibleRange}" />
            </s:SciChartSurface.YAxis>

            <s:SciChartSurface.XAxis>
                <s:NumericAxis AutoRange="{Binding AxisXRangeMode}" 
                               BorderBrush="{StaticResource BorderBrushGray}" 
                               BorderThickness="1" 
                               DrawMajorBands="False" 
                               DrawMinorGridLines="False" 
                               DrawMajorGridLines="True" 
                               DrawMajorTicks="False" 
                               DrawMinorTicks="False" 
                               TextFormatting="0" 
                               VisibleRange="{Binding SharedXVisibleRange, Mode=TwoWay}" 
                               s:VerticalSliceModifier.AxisLabelContainerStyle="{x:Null}"/>
            </s:SciChartSurface.XAxis>

            <!--  Modifiers  -->
            <s:SciChartSurface.ChartModifier>
                <s:ModifierGroup>
                    <s:RubberBandXyZoomModifier 
                        IsXAxisOnly="True" 
                        ZoomExtentsY="True" 
                        IsAnimated="True" 
                        RubberBandFill="#20FFFFFF" 
                        RubberBandStroke="GreenYellow" 
                        RubberBandStrokeDashArray="2 2">
                    </s:RubberBandXyZoomModifier>

                    <s:ZoomExtentsModifier IsAnimated="True"/>

                    <s:MouseWheelZoomModifier IsEnabled="True"/>

                    <s:XAxisDragModifier IsEnabled="True" DragMode="Pan"/>

                    <s:LegendModifier x:Name="legendModifier"
                                      Background="Transparent" 
                                      Margin="10" 
                                      GetLegendDataFor="AllSeries" 
                                      LegendItemTemplate="{StaticResource CustomLegendTemplate}" 
                                      ShowLegend="True" ShowVisibilityCheckboxes="True"/>

                    <s:VerticalSliceModifier Name="sliceModifier">

                    <s:VerticalSliceModifier.VerticalLines>
                            <s:VerticalLineAnnotation Style="{StaticResource sliceStyle}" 
                                                      X1="{Binding SlicePosition, Mode=TwoWay}"/>
                        </s:VerticalSliceModifier.VerticalLines>
                    </s:VerticalSliceModifier>

                </s:ModifierGroup>
            </s:SciChartSurface.ChartModifier>
        </s:SciChartSurface>

Thanks in advance,
Declan.

PS. I’m trying to attach a screenshot but it keeps saying “Forbidden”.

Hello,
I am trying to add a BoxAnnotation with MVVM pattern where the X-Axis is a DateTime axis. The annotation can be dragged into the X-direction. I need to know the DateTime of each position while dragging and also the final position(DateTime) of the BoxAnnotation when the drag Ended. I am listening to the DragDelta and DragEnded events in ViewModel. But here I couldn’t able to get the DateTime from X1 and X2 of that annotation model. I am sharing some snippets of my code. Can you please let me know how I can achieve this?

In xaml:

<Style x:Key="_boxAnnotationStyle" BasedOn="{StaticResource AnnotationBaseStyle}" TargetType="scichart:BoxAnnotation">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="scichart:BoxAnnotation">
                    <Border x:Name="PART_BoxAnnotationRoot"
              Margin="{TemplateBinding Margin}"
              Background="{TemplateBinding Background}"
              BorderBrush="{TemplateBinding BorderBrush}"
              BorderThickness="{TemplateBinding BorderThickness}"
              CornerRadius="{TemplateBinding CornerRadius}" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
</Style>
<scichart:SciChartSurface x:Name="GraphSurface"
                 Annotations="{scichart:AnnotationsBinding ItsAnnotations}">

                <scichart:SciChartSurface.XAxis>
                    <scichart:DateTimeAxis x:Name="GraphXAxis"
                                           VisibleRange="{Binding ItsTimeVisibleRange, Mode=TwoWay}" />
                </scichart:SciChartSurface.XAxis>

                <scichart:SciChartSurface.YAxes>
                    <scichart:NumericAxis x:Name="GraphYAxis"
                                          VisibleRange="0, 10" />

                </scichart:SciChartSurface.YAxes>
 </scichart:SciChartSurface>

In ViewModel.cs

{
    private DateRange _timeVisibleRange;
    private ObservableCollection<IAnnotationViewModel> _annotations;
    private IAnnotationViewModel _boxAnnotation;
    public ObservableCollection<IAnnotationViewModel> ItsAnnotations
    {
        get
        {
            return _annotations;
        }
    }
    public DateRange ItsTimeVisibleRange
    {
        get { return _timeVisibleRange; }
        set
        {
            if (_timeVisibleRange == value) return;
            _timeVisibleRange = value;
            RaisePropertyChanged(() => ItsTimeVisibleRange);
        }
    }
    .
    .
    .
    _boxAnnotation = new BoxAnnotationViewModel()
        {
            IsEditable = true,
            DragDirections = SciChart.Charting.XyDirection.XDirection,
            X1 = DateTime.UtcNow.AddSeconds(300),
            X2 = DateTime.UtcNow,
            Y1 = 0,
            Y2 = 8,
            StyleKey = "_boxAnnotationStyle"
        };

     _annotations = new ObservableCollection<IAnnotationViewModel>() { };
     _annotations.Add(_boxAnnotation );

     _captureTimeRangeSelectorAnnotation.DragDelta += OnDrag;
     _captureTimeRangeSelectorAnnotation.DragEnded += DragEnded;
       .
       .
       .
    private void DragEnded(object sender, EventArgs e)
    {
         var boxAnnotationModel = sender as BoxAnnotationViewModel;
          // Need to know the DateTime value of X1 and X2
    }
    private void OnDrag(object sender, AnnotationDragDeltaEventArgs e)
    {
         var boxAnnotationModel = sender as BoxAnnotationViewModel;
         // Need to know the DateTime value of X1 and X2
    }
    .....
    .....
}