WebChartControl.LegendItemChecked Event

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

Namespace: DevExpress.XtraCharts.Web

Assembly: DevExpress.XtraCharts.v20.2.Web.dll

NuGet Package: DevExpress.Web.Visualization

Declaration

C#

public event LegendItemCheckedEventHandler LegendItemChecked

VB.NET

Public Event LegendItemChecked As LegendItemCheckedEventHandler

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

MainForm.cs

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;
        }
    }
}

MainForm.vb

Imports Microsoft.VisualBasic
Imports System
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms
Imports DevExpress.XtraCharts

Namespace CustomCheckboxesInLegendViewAndBehavior
    Partial Public Class mainForm
        Inherits Form
        Private Const LegendRadioSide As Integer = 17
        Private Const LegendRadioInnerPointBoundsSide As Integer = 8
        Private Const LegendRadioWidth As Single = 1.5F
        Private initializationFlag As Boolean = False

        Public Sub New()
            InitializeComponent()
            initializationFlag = True
            chartControl.BeginInit()
            chartControl.Legend.UseCheckBoxes = True
            AddHandler chartControl.CustomDrawSeries, AddressOf OnCustomDrawSeries
            AddHandler chartControl.LegendItemChecked, AddressOf OnLegendItemChecked
            chartControl.Series("Point").CheckedInLegend = True
            chartControl.Series("Line").CheckedInLegend = False
            chartControl.Series("Area").CheckedInLegend = False
            chartControl.EndInit()
            initializationFlag = False
        End Sub

        Private Sub OnLegendItemChecked(ByVal sender As Object, ByVal e As LegendItemCheckedEventArgs)
            If initializationFlag = True Then
                Return
            End If
            initializationFlag = True
            Dim checkedSeries As Series = TryCast(e.CheckedElement, Series)
            If checkedSeries Is Nothing Then
                Throw New Exception("Expected series only")
            End If
            For Each series As Series In chartControl.Series
                series.CheckedInLegend = False
            Next series
            checkedSeries.CheckedInLegend = True
            chartControl.Titles(0).Text = checkedSeries.Name
            initializationFlag = False
        End Sub

        Private Sub OnCustomDrawSeries(ByVal sender As Object, ByVal e As CustomDrawSeriesEventArgs)
            Dim bitmap As New Bitmap(LegendRadioSide, LegendRadioSide)
            Using graphics As Graphics = graphics.FromImage(bitmap)
                graphics.SmoothingMode = SmoothingMode.HighQuality
                Dim seriesColor As Color = GetSeriesColor(e.Series, chartControl)
                Dim radioPen As New Pen(seriesColor, LegendRadioWidth)
                Dim radioRadius As Integer = LegendRadioSide - 3
                Dim radioRectangle As New Rectangle(1, 1, radioRadius, radioRadius)
                graphics.DrawEllipse(radioPen, radioRectangle)
                If e.Series.CheckedInLegend Then
                    Dim brush As Brush = New SolidBrush(seriesColor)
                    Dim coord As Integer = (LegendRadioSide - LegendRadioInnerPointBoundsSide) / 2
                    Dim filledEllipseBounds As New Rectangle(coord, coord, LegendRadioInnerPointBoundsSide, LegendRadioInnerPointBoundsSide)
                    graphics.FillEllipse(brush, filledEllipseBounds)
                End If
            End Using
            e.DisposeLegendMarkerImage = True
            e.LegendMarkerImage = bitmap
        End Sub
        Private Function GetSeriesColor(ByVal series As Series, ByVal chartControlDistributions As ChartControl) As Color
            Dim seriesIndex As Integer = chartControlDistributions.Series.IndexOf(series)
            Dim paletteName As String = chartControlDistributions.PaletteName
            Dim currentPalette As Palette = chartControlDistributions.PaletteRepository(paletteName)
            Dim paletteEntryAccordingToSeries As PaletteEntry = currentPalette(seriesIndex)
            Dim result As Color = paletteEntryAccordingToSeries.Color
            Return result
        End Function
    End Class
End Namespace

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the LegendItemChecked event.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

how-to-preserve-the-legend-checkbox-item-state-when-the-series-items-are-created-manually-t470764/CS/dxSample/Default.aspx.cs#L26

chartControl.SaveStateOnCallbacks = false;
chartControl.LegendItemChecked += chartControl_LegendItemChecked;
return chartControl;

VB.NET

how-to-preserve-the-legend-checkbox-item-state-when-the-series-items-are-created-manually-t470764/VB/dxSample/Default.aspx.vb#L28

chartControl.SaveStateOnCallbacks = False
AddHandler chartControl.LegendItemChecked, AddressOf chartControl_LegendItemChecked
Return chartControl