WebChartControl.LegendItemChecked Event

Occurs when a legend item is checked in the legend check box.

Namespace: DevExpress.XtraCharts.Web

Assembly: DevExpress.XtraCharts.v21.1.Web.dll

Declaration

public event LegendItemCheckedEventHandler LegendItemChecked

Event Data

The LegendItemChecked event's data class is LegendItemCheckedEventArgs. The following properties provide information specific to this event:

Property Description
CheckedElement Gets a value that defines which chart element has been checked on a legend by a legend check box.
NewCheckState Gets a value that indicates the check state of a legend item after the ChartControl.LegendItemChecked event is handled.

Remarks

The LegendItemChecked event is raised after the legend item has been checked in the legend check box by an end-user or in code by setting the CheckedInLegend property to true for the corresponding chart element.

Example

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.

View Example

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