LegendItemCheckedEventArgs.CheckedElement Property

Gets a value that defines which chart element has been checked on a legend by a legend check box.

Namespace: DevExpress.XtraCharts

Assembly: DevExpress.XtraCharts.v20.1.dll

Declaration

public ChartElement CheckedElement { get; }
Public ReadOnly Property CheckedElement As ChartElement

Property Value

Type Description
ChartElement

The ChartElement value that is the chart element for which the legend check box has been checked.

Remarks

Use the CheckedElement property to define a chart element for which the legend check box has been checked when the ChartControl.LegendItemChecked (WebChartControl.LegendItemChecked) event is handled.

NOTE

Set the Legend.UseCheckBoxes property to CheckBox, CheckBoxAndMarker or MarkerAndCheckBox to use legend check boxes.

For more information on legend check boxes, see the corresponding section of the Legend Check Box topic.

Examples

This example demonstrates how to show a series (Point, Line or Area), depending on the selection state of a custom radio button in the chart legend.

To accomplish this task, do the following:

Use the ChartControl.CustomDrawSeries (WebChartControl.CustomDrawSeries) event handler to create a custom appearance for radio buttons based on the color of a selected series.

To provide the capability for custom radio buttons to show (or hide) the series, use the LegendItemCheckedEventArgs.CheckedElement and SeriesBase.CheckedInLegend properties in the ChartControl.LegendItemChecked (WebChartControl.LegendItemChecked) event.


using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
using DevExpress.XtraCharts;

namespace CustomCheckboxesInLegendViewAndBehavior {
    public partial class mainForm : Form {
        const int LegendRadioSide = 17;
        const int LegendRadioInnerPointBoundsSide = 8;
        const float LegendRadioWidth = 1.5f;
        bool initializationFlag = false;

        public mainForm() {
            InitializeComponent();
            chartControl.BeginInit();
            {
                chartControl.LegendItemChecked += OnLegendItemChecked;
                chartControl.CustomDrawSeries += OnCustomDrawSeries;
                chartControl.Legend.UseCheckBoxes = true;
                chartControl.Series["Point"].CheckedInLegend = false;
                chartControl.Series["Line"].CheckedInLegend = true;
                chartControl.Series["Area"].CheckedInLegend = false;
            }
            chartControl.EndInit();
            initializationFlag = false;
        }

        void OnLegendItemChecked(object sender, LegendItemCheckedEventArgs e) {
            if (initializationFlag == true)
                return;
            initializationFlag = true;
            {
                Series checkedSeries = e.CheckedElement as Series;
                if (checkedSeries == null)
                    throw new Exception("Expected series only");
                foreach (Series series in chartControl.Series)
                    series.CheckedInLegend = false;
                checkedSeries.CheckedInLegend = true;
                chartControl.Titles[0].Text = checkedSeries.Name;
            }
            initializationFlag = false;
        }

        void OnCustomDrawSeries(object sender, CustomDrawSeriesEventArgs e) {
            Bitmap bitmap = new Bitmap(LegendRadioSide, LegendRadioSide);
            using (Graphics graphics = Graphics.FromImage(bitmap)) {
                graphics.SmoothingMode = SmoothingMode.HighQuality;
                Color seriesColor = GetSeriesColor(e.Series, chartControl);
                Pen radioPen = new Pen(seriesColor, LegendRadioWidth);
                int radioRadius = LegendRadioSide - 3;
                Rectangle radioRectangle = new Rectangle(1, 1, radioRadius, radioRadius);
                graphics.DrawEllipse(radioPen, radioRectangle);
                if (e.Series.CheckedInLegend) {
                    Brush brush = new SolidBrush(seriesColor);
                    int coord = (LegendRadioSide - LegendRadioInnerPointBoundsSide) / 2;
                    Rectangle filledEllipseBounds = new Rectangle(coord, coord,
                          LegendRadioInnerPointBoundsSide, LegendRadioInnerPointBoundsSide);
                    graphics.FillEllipse(brush, filledEllipseBounds);
                }
            }
            e.DisposeLegendMarkerImage = true;
            e.LegendMarkerImage = bitmap;
        }

        Color GetSeriesColor(Series series, ChartControl chartControl) {
            int seriesIndex = chartControl.Series.IndexOf(series);
            string paletteName = chartControl.PaletteName;
            Palette currentPalette = chartControl.PaletteRepository[paletteName];
            PaletteEntry paletteEntryAccordingToSeries = currentPalette[seriesIndex];
            Color result = paletteEntryAccordingToSeries.Color;
            return result;
        }
    }
}
See Also