[Solved] Using InteractivitySettings with an Aggregate doesn't work correctly

[Scott]

I have the following chart defined below that uses an InteractivitySettings SelectionMode of Single and an ItemMapping with an aggregate function of Sum. Every bar the user clicks on gets selected so the items selected will go past one.

If I remove the aggregate summation then it works fine.

<telerik:RadChart x:Class="Fieldnotebook.Controls.BarChartControl"
    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:telerik="http://schemas.telerik.com/2008/xaml/presentation"
    mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="400"
    ItemsSource="{Binding Path=View}">

    <telerik:RadChart.SeriesMappings>
        <telerik:SeriesMapping>
            <telerik:SeriesMapping.SeriesDefinition>
                <telerik:BarSeriesDefinition>
                    <telerik:BarSeriesDefinition.InteractivitySettings>
                        <telerik:InteractivitySettings  SelectionMode="Single" SelectionScope="Item" />
                    </telerik:BarSeriesDefinition.InteractivitySettings>
                </telerik:BarSeriesDefinition>
            </telerik:SeriesMapping.SeriesDefinition>
            <telerik:SeriesMapping.GroupingSettings>
                <telerik:GroupingSettings ShouldCreateSeriesForLastGroup="True">
                    <telerik:GroupingSettings.GroupDescriptors>
                        <telerik:ChartGroupDescriptor Member="ActivityGroupDescription" />
                    </telerik:GroupingSettings.GroupDescriptors>
                </telerik:GroupingSettings>
            </telerik:SeriesMapping.GroupingSettings>
            <telerik:SeriesMapping.ItemMappings>
                <telerik:ItemMapping FieldName="Rate" DataPointMember="YValue" AggregateFunction="Sum" />
            </telerik:SeriesMapping.ItemMappings>
        </telerik:SeriesMapping>
    </telerik:RadChart.SeriesMappings>

    <telerik:RadChart.DefaultView>
        <telerik:ChartDefaultView>
            <telerik:ChartDefaultView.ChartLegend>
                <telerik:ChartLegend x:Name="GroupLegend2"  UseAutoGeneratedItems="True" />
            </telerik:ChartDefaultView.ChartLegend>

            <telerik:ChartDefaultView.ChartArea>
                <telerik:ChartArea LegendName="GroupLegend2" SelectionChanged="ChartArea_SelectionChanged">
                    <telerik:ChartArea.AxisX>
                        <telerik:AxisX AutoRange="True" DefaultLabelFormat="0.0" Title="Activity Group" AxisLabelsVisibility="Collapsed" />
                    </telerik:ChartArea.AxisX>
                    <telerik:ChartArea.AxisY>
                        <telerik:AxisY AutoRange="True" DefaultLabelFormat="0" Title="Amount (Sum)"/>
                    </telerik:ChartArea.AxisY>
                </telerik:ChartArea>
            </telerik:ChartDefaultView.ChartArea>
        </telerik:ChartDefaultView>
    </telerik:RadChart.DefaultView>
</telerik:RadChart>

[Scott]

I worked around the problem by doing this:

private void ChartArea_SelectionChanged(object sender, ChartSelectionChangedEventArgs e)
{
    ChartArea chartArea = (ChartArea)sender;

    chartArea.SelectionChanged -= ChartArea_SelectionChanged;
    try
    {
        IList<DataPoint> dataPoints = e.AddedItems;
        if (dataPoints.Count == 1)
        {
            DataPoint dataPoint = dataPoints.First();
            chartArea.ClearSelection();
            chartArea.SelectItem(dataPoint);
        }
    }
    finally
    {
        chartArea.SelectionChanged += ChartArea_SelectionChanged;
    }
}

[Yavor]

Hello Scott,

Let me explain first how the selection mode works. When SelectionScope is set to InteractivityScope.Item, when one selects a bar item, only the respective item will be highlighted (i.e. all of the other series as well all of the other bar items within the originating bar series will become temporarily transparent). In your scenario you are grouping your chart and this creates a new data series for each group. Using sum aggregation function you are reducing the number of items in each series to only 1. That's why you can select more than one item.

The solution can be to flatten the result to a single series. This way the selection interactivity will work as expected. Your code can look like this:

<telerik:SeriesMapping.GroupingSettings>
    <telerik:GroupingSettings ShouldCreateSeriesForLastGroup="True" ShouldFlattenSeries="True">
        <telerik:GroupingSettings.GroupDescriptors>
            <telerik:ChartGroupDescriptor Member="ActivityGroupDescription" />
        </telerik:GroupingSettings.GroupDescriptors>
    </telerik:GroupingSettings>
</telerik:SeriesMapping.GroupingSettings>

I have attached a sample application using your code that uses this solution.
Hope this helps!

All the best,
Yavor Ivanov
the Telerik team

[Scott]

Thank you very much for the explanation. I'll give it a try.