Selection

• Oct 14, 2020
• 4 minutes to read

Use the mouse or touch gestures on touchscreen devices to select series and series points.

Selection Mode

The ChartControl.SelectionMode property value defines whether you can select chart elements. When this property’s value is set to None (default value), end users cannot select a chart’s elements. The ElementSelectionMode enumeration lists all the selection modes. To enable selection, set the SelectionMode property to one of the following modes:

Mode	Example	Description
Single		Only one series element can be selected. Click or tap a series element to select it. Set the ChartControl.SelectionMode property to ElementSelectionMode.Single to enable this mode.
Multiple		You can select multiple series elements simultaneously. Click or tap a series element to select it. Hold Ctrl and click a series element to deselect it. In this mode, you can also use the Selection Rectangle to select multiple series’s elements. Move the mouse pointer while the Ctrl key and the left mouse button are pressed to mark series elements to be selected. Set the ChartControl.SelectionMode property to ElementSelectionMode.Multiple to enable this mode.
Extended		The Extended mode combines the Single and Multiple selection modes’ behaviors. Click an element to select it. To select/deselect multiple elements, click them while the Ctrl key is pressed. Set the ChartControl.SelectionMode property to ElementSelectionMode.Extended to enable this mode.

Series Selection Mode

The ChartControl.SeriesSelectionMode property specifies a series element that is selected when you click a series point. The SeriesSelectionMode enumeration contains all possible modes.

Mode	Example	Description
Point (default mode)		You can select only one series point at a time. Set the ChartControl.SeriesSelectionMode property to SeriesSelectionMode.Point to enable this mode.
Argument		This mode allows you to select points with the same argument simultaneously. Set the ChartControl.SeriesSelectionMode property to SeriesSelectionMode.Argument to enable this mode.
Series		In this mode, click a series point to select the entire series. Set the ChartControl.SeriesSelectionMode property to SeriesSelectionMode.Series to enable this mode.

Access the Selected Elements

Use the ChartControl.SelectedItem or ChartControl.SelectedItems properties to access the selected elements.

XAML

<dxc:ChartControl SelectionMode="Single"
                  SelectedItem="{Binding Path=SelectedCountry, Mode=TwoWay}">
        <!-- Other Chart Control's settings. -->
</dxc:ChartControl>

View Example: How to implement selection in the MVVM style

Specify Selection Rectangle’s Appearance

Assign a DataTemplate object to the XYDiagram2D.SelectionTemplate property to specify the Selection Rectangle’s appearance:

XAML

<dxc:XYDiagram2D EnableAxisXNavigation="True" 
                 EnableAxisYNavigation="True">
    <dxc:XYDiagram2D.SelectionTemplate>
        <DataTemplate>
            <Border BorderThickness="1" BorderBrush="Gray">
                <Rectangle Opacity="0.3" Fill="Gray"/>
            </Border>
        </DataTemplate>
    </dxc:XYDiagram2D.SelectionTemplate>
    <!--...-->
</dxc:XYDiagram2D>

Customize the Appearance of Selected Series Points

Use a custom series model to change the appearance of selected series points.

To change the color of selected series points, follow the steps below:

• Implement a custom model of a particular series (CustomBar2DModel in the example below).

• Create a ControlTemplate object and assign it to the CustomBar2DModel.PointTemplate property.

• Create the IsSelectedToBrushConverter class that implements the IValueConverter interface and contains the Convert and ConvertBack methods. The Convert method returns different colors for selected and unselected series points.

• Bind the Border.Background property to the IsSelected property and use the IsSelectedToBrushConverter object to convert the IsSelected value to a color.

XAML

 <Window.Resources>
        <ResourceDictionary>
            <local:IsSelectedToBrushConverter x:Key="isSelectedConverter"/>
        </ResourceDictionary>
    </Window.Resources>
    <Grid>
        <dxc:ChartControl  SelectionMode="Multiple"  CrosshairEnabled="False">
            <dxc:ChartControl.Diagram>
                <dxc:XYDiagram2D>
                    <dxc:XYDiagram2D.Series>
                        <dxc:BarSideBySideSeries2D>
                            <dxc:BarSideBySideSeries2D.Model>
                                <dxc:CustomBar2DModel>
                                    <dxc:CustomBar2DModel.PointTemplate>
                                        <ControlTemplate>
                                            <Border Background="{Binding IsSelected, Converter={StaticResource isSelectedConverter}}"/>
                                        </ControlTemplate>
                                    </dxc:CustomBar2DModel.PointTemplate>
                                </dxc:CustomBar2DModel>
                            </dxc:BarSideBySideSeries2D.Model>
                            <!--...-->
                        </dxc:BarSideBySideSeries2D>
                    </dxc:XYDiagram2D.Series>
                </dxc:XYDiagram2D>
            </dxc:ChartControl.Diagram>
        </dxc:ChartControl>
    </Grid>
</Window>

C#

 public class IsSelectedToBrushConverter : IValueConverter {

    public object Convert(object value, System.Type targetType, object parameter, CultureInfo culture) {
        if (value is bool && targetType == typeof(Brush)) {
            bool isSelected = (bool)value;
            return isSelected ? Brushes.Black : Brushes.Red;
        }
        return null;
    }

    public object ConvertBack(object value, System.Type targetType, object parameter, CultureInfo culture) {
        throw new System.NotImplementedException();
    }
}

VB.NET

Public Class IsSelectedToBrushConverter
    Inherits IValueConverter

    Public Function Convert(ByVal value As Object, ByVal targetType As System.Type, ByVal parameter As Object, ByVal culture As CultureInfo) As Object
        If TypeOf value Is Boolean AndAlso targetType = GetType(Brush) Then
            Dim isSelected As Boolean = CBool(value)
            Return If(isSelected, Brushes.Black, Brushes.Red)
        End If

        Return Nothing
    End Function

    Public Function ConvertBack(ByVal value As Object, ByVal targetType As System.Type, ByVal parameter As Object, ByVal culture As CultureInfo) As Object
        Throw New System.NotImplementedException()
    End Function
End Class

View Example: How to customize the appearance of selected series points