Allow Line Selection in RadChartView LineSeries

Environment

Product	Version
RadChartView for WPF	2024.1.423

Description

The built-in selection feature of RadChartView allows you to select data points in the chart by clicking the corresponding data point visuals.

This article describes how to implement custom selection logic activated on clicking over the LineSeries' line. The selection will highlight the series with a different Stroke setting.

Solution

The chart's LineSeries already has a selection infrastructure that can be used to mark the line as selected. To do that, set the AllowSelect and IsSelected properties of the series to true.

The selection state can be toggled in the MouseLeftButtonDown event of the chart.

The highlighting of the series can be implemented either in the mouse event handler or with a trigger (as shown in this example) or another WPF method. Basically, on mouse click, the Stroke property of the corresponding LineSeries should be updated.

The following example shows how to combine these suggestions.

Defining the chart and setting up the highlighting

<telerik:RadCartesianChart MouseLeftButtonDown="RadCartesianChart_MouseLeftButtonDown"> 
    <telerik:RadCartesianChart.Resources> 
        <!-- in case the NoXaml dlls are used, add the following setting to the Style object --> 
        <!-- BasedOn="{StaticResource LineSeriesStyle}" --> 
        <Style TargetType="telerik:LineSeries"> 
            <Setter Property="AllowSelect" Value="True"/> 
            <Setter Property="Cursor" Value="Hand" /> 
            <Setter Property="Stroke" Value="#95C74C" /> 
            <Setter Property="StrokeThickness" Value="3" /> 
            <Style.Triggers> 
                <Trigger Property="IsSelected" Value="True"> 
                    <Setter Property="Stroke" Value="#3c5c0d" /> 
                </Trigger> 
            </Style.Triggers> 
        </Style> 
    </telerik:RadCartesianChart.Resources> 
    <telerik:RadCartesianChart.HorizontalAxis> 
        <telerik:CategoricalAxis/> 
    </telerik:RadCartesianChart.HorizontalAxis> 
    <telerik:RadCartesianChart.VerticalAxis> 
        <telerik:LinearAxis /> 
    </telerik:RadCartesianChart.VerticalAxis> 
    <telerik:RadCartesianChart.Series> 
        <telerik:LineSeries> 
            <telerik:LineSeries.DataPoints> 
                <telerik:CategoricalDataPoint Category="January" Value="2" /> 
                <telerik:CategoricalDataPoint Category="February" Value="5" /> 
                <telerik:CategoricalDataPoint Category="March" Value="3" /> 
                <telerik:CategoricalDataPoint Category="April" Value="10" /> 
                <telerik:CategoricalDataPoint Category="May" Value="9" /> 
                <telerik:CategoricalDataPoint Category="June" Value="7" /> 
                <telerik:CategoricalDataPoint Category="July" Value="1" /> 
            </telerik:LineSeries.DataPoints> 
        </telerik:LineSeries> 
        <telerik:LineSeries> 
            <telerik:LineSeries.DataPoints> 
                <telerik:CategoricalDataPoint Category="January" Value="4" /> 
                <telerik:CategoricalDataPoint Category="February" Value="4" /> 
                <telerik:CategoricalDataPoint Category="March" Value="4" /> 
                <telerik:CategoricalDataPoint Category="April" Value="2" /> 
                <telerik:CategoricalDataPoint Category="May" Value="5" /> 
                <telerik:CategoricalDataPoint Category="June" Value="5" /> 
                <telerik:CategoricalDataPoint Category="July" Value="8" /> 
            </telerik:LineSeries.DataPoints> 
        </telerik:LineSeries> 
    </telerik:RadCartesianChart.Series> 
</telerik:RadCartesianChart> 

Implementing the MouseLeftButtonDown handler

private void RadCartesianChart_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) 
{ 
    var chart = (RadCartesianChart)sender; 
    var lineSeries = chart.Series.OfType<LineSeries>(); 
 
    if (lineSeries.Any(x => x.IsMouseOver)) 
    { 
        foreach (var series in lineSeries) 
        { 
            series.IsSelected = series.IsMouseOver ? (series.IsSelected ^ true) : false;                     
        } 
    }        
}