Hide/Show a Chart Series by Clicking a Legend Item

Environment

Product Version	Product	Author
2019.1.219	RadChartView for WinForms	Desislava Yordanova

Description

This article aims to show you a sample approach how to hide/show a chart series by clicking its legend item.

Solution

It is necessary to handle the Click event of each LegendItemElement and manipulate the visibility of the associated chart series. Handling the MouseEnter event of RadChartView and setting the ItemCapture to null ensures that the chart is focused as soon as you move the mouse cursor over the chart:

Hide/Show chart series from legend items

        public RadForm1()
        {
            InitializeComponent();

            LineSeries lineSeries = new LineSeries();
            lineSeries.LegendTitle = "First";
            lineSeries.DataPoints.Add(new CategoricalDataPoint(20, "Jan"));
            lineSeries.DataPoints.Add(new CategoricalDataPoint(22, "Apr"));
            lineSeries.DataPoints.Add(new CategoricalDataPoint(12, "Jul"));
            lineSeries.DataPoints.Add(new CategoricalDataPoint(19, "Oct"));
            this.radChartView1.Series.Add(lineSeries);
            LineSeries lineSeries2 = new LineSeries();
            lineSeries2.LegendTitle = "Second";
            lineSeries2.DataPoints.Add(new CategoricalDataPoint(18, "Jan"));
            lineSeries2.DataPoints.Add(new CategoricalDataPoint(15, "Apr"));
            lineSeries2.DataPoints.Add(new CategoricalDataPoint(17, "Jul"));
            lineSeries2.DataPoints.Add(new CategoricalDataPoint(22, "Oct"));
            this.radChartView1.Series.Add(lineSeries2);

            this.radChartView1.ShowLegend = true;

            foreach (LegendItemElement item in this.radChartView1.ChartElement.LegendElement.StackElement.Children)
            {
                item.TitleElement.Click += TitleElement_Click;
            }
            this.radChartView1.MouseEnter += radChartView1_MouseEnter;
        }

        private void radChartView1_MouseEnter(object sender, EventArgs e)
        {
            this.radChartView1.Behavior.ItemCapture = null;
        }

        private void TitleElement_Click(object sender, EventArgs e)
        {
            LegendItemTitle title = sender as LegendItemTitle;
            LegendItemElement itemElement = title.Parent as LegendItemElement;
            itemElement.LegendItem.Element.IsVisible = !itemElement.LegendItem.Element.IsVisible;
            if (!itemElement.LegendItem.Element.IsVisible)
            {
                title.Opacity = 0.5;
            }
            else
            {
                title.Opacity = 1;
            }
        }

    Sub New()

        InitializeComponent()

        Dim lineSeries As New LineSeries()
        lineSeries.LegendTitle = "First"
        lineSeries.DataPoints.Add(New CategoricalDataPoint(20, "Jan"))
        lineSeries.DataPoints.Add(New CategoricalDataPoint(22, "Apr"))
        lineSeries.DataPoints.Add(New CategoricalDataPoint(12, "Jul"))
        lineSeries.DataPoints.Add(New CategoricalDataPoint(19, "Oct"))
        Me.RadChartView1.Series.Add(lineSeries)
        Dim lineSeries2 As New LineSeries()
        lineSeries2.LegendTitle = "Second"
        lineSeries2.DataPoints.Add(New CategoricalDataPoint(18, "Jan"))
        lineSeries2.DataPoints.Add(New CategoricalDataPoint(15, "Apr"))
        lineSeries2.DataPoints.Add(New CategoricalDataPoint(17, "Jul"))
        lineSeries2.DataPoints.Add(New CategoricalDataPoint(22, "Oct"))
        Me.RadChartView1.Series.Add(lineSeries2)

        Me.RadChartView1.ShowLegend = True

        For Each item As LegendItemElement In Me.RadChartView1.ChartElement.LegendElement.StackElement.Children
            AddHandler item.TitleElement.Click, AddressOf TitleElement_Click
        Next

        AddHandler Me.RadChartView1.MouseEnter, AddressOf RadChartView_MouseEnter
    End Sub

    Private Sub RadChartView_MouseEnter(sender As Object, e As EventArgs)
        Me.RadChartView1.Behavior.ItemCapture = Nothing
    End Sub

    Private Sub TitleElement_Click(sender As Object, e As EventArgs)
        Dim title As LegendItemTitle = TryCast(sender, LegendItemTitle)
        Dim itemElement As LegendItemElement = TryCast(title.Parent, LegendItemElement)
        itemElement.LegendItem.Element.IsVisible = Not itemElement.LegendItem.Element.IsVisible
        If Not itemElement.LegendItem.Element.IsVisible Then
            title.Opacity = 0.5
        Else
            title.Opacity = 1
        End If
    End Sub