Apply a Custom Shape to ChartView's Legend Items

Environment

Product Version	Product	Author
2019.2.508	RadChartView for WinForms	Desislava Yordanova

Description

The LegendItemElement in RadChartView consists of a LegendItemTitle and a LegendItemMarker:

A common requirement is to change the square shape of the marker element. This article demonstrates how to achieve it.

Solution

Before populating RadChartView with data, subscribe to the ChartElement.LegendElement.VisualItemCreating event, create the default LegendItemElement and assign an ElementShape to the ItemElement.MarkerElement.Shape property:

Apply a HeartShape to legend items

        public RadForm1()
        {
            InitializeComponent();

            this.radChartView1.ChartElement.LegendElement.VisualItemCreating += LegendElement_VisualItemCreating;

            BarSeries barSeries = new BarSeries("Performance", "RepresentativeName");
            barSeries.LegendTitle = "Q1";
            barSeries.DataPoints.Add(new CategoricalDataPoint(177, "Harley"));
            barSeries.DataPoints.Add(new CategoricalDataPoint(128, "White"));
            barSeries.DataPoints.Add(new CategoricalDataPoint(143, "Smith"));
            barSeries.DataPoints.Add(new CategoricalDataPoint(111, "Jones"));
            barSeries.DataPoints.Add(new CategoricalDataPoint(118, "Marshall"));
            this.radChartView1.Series.Add(barSeries);
            BarSeries barSeries2 = new BarSeries("Performance", "RepresentativeName");
            barSeries2.LegendTitle = "Q2";
            barSeries2.DataPoints.Add(new CategoricalDataPoint(153, "Harley"));
            barSeries2.DataPoints.Add(new CategoricalDataPoint(141, "White"));
            barSeries2.DataPoints.Add(new CategoricalDataPoint(130, "Smith"));
            barSeries2.DataPoints.Add(new CategoricalDataPoint(88, "Jones"));
            barSeries2.DataPoints.Add(new CategoricalDataPoint(109, "Marshall"));
            this.radChartView1.Series.Add(barSeries2);

            this.radChartView1.ShowLegend = true;
        }

        private void LegendElement_VisualItemCreating(object sender, LegendItemElementCreatingEventArgs e)
        {
            e.ItemElement = new LegendItemElement(e.LegendItem);
            e.ItemElement.MarkerElement.Shape = new HeartShape();
        }

       Public Sub New()
        InitializeComponent()
        AddHandler Me.RadChartView1.ChartElement.LegendElement.VisualItemCreating, AddressOf LegendElement_VisualItemCreating
        Dim barSeries As BarSeries = New BarSeries("Performance", "RepresentativeName")
        barSeries.LegendTitle = "Q1"
        barSeries.DataPoints.Add(New CategoricalDataPoint(177, "Harley"))
        barSeries.DataPoints.Add(New CategoricalDataPoint(128, "White"))
        barSeries.DataPoints.Add(New CategoricalDataPoint(143, "Smith"))
        barSeries.DataPoints.Add(New CategoricalDataPoint(111, "Jones"))
        barSeries.DataPoints.Add(New CategoricalDataPoint(118, "Marshall"))
        Me.RadChartView1.Series.Add(barSeries)
        Dim barSeries2 As BarSeries = New BarSeries("Performance", "RepresentativeName")
        barSeries2.LegendTitle = "Q2"
        barSeries2.DataPoints.Add(New CategoricalDataPoint(153, "Harley"))
        barSeries2.DataPoints.Add(New CategoricalDataPoint(141, "White"))
        barSeries2.DataPoints.Add(New CategoricalDataPoint(130, "Smith"))
        barSeries2.DataPoints.Add(New CategoricalDataPoint(88, "Jones"))
        barSeries2.DataPoints.Add(New CategoricalDataPoint(109, "Marshall"))
        Me.RadChartView1.Series.Add(barSeries2)
        Me.RadChartView1.ShowLegend = True
    End Sub

    Private Sub LegendElement_VisualItemCreating(ByVal sender As Object, ByVal e As LegendItemElementCreatingEventArgs)
        e.ItemElement = New LegendItemElement(e.LegendItem)
        e.ItemElement.MarkerElement.Shape = New HeartShape()
    End Sub

You can also create your own ElementShape. Create a derivative of the ElementShape class and override its CreatePath method. The following code snippet demonstrates how to draw a single line as it is demonstrated below:

Apply a custom LineShape to legend items

        private void LegendElement_VisualItemCreating(object sender, LegendItemElementCreatingEventArgs e)
        {
            e.ItemElement = new LegendItemElement(e.LegendItem);
            e.ItemElement.MarkerElement.Shape = new LineShape();
        }

        public class LineShape : ElementShape
        {
            public override GraphicsPath CreatePath(Rectangle bounds)
            {
                GraphicsPath path = new GraphicsPath();

                Point start = new Point(bounds.X, bounds.Y);
                Point end = new Point(bounds.X + bounds.Width, bounds.Y);
                path.AddLine(start, end);
                return path;
            }
        }

    Private Sub LegendElement_VisualItemCreating(ByVal sender As Object, ByVal e As LegendItemElementCreatingEventArgs)
        e.ItemElement = New LegendItemElement(e.LegendItem)
        e.ItemElement.MarkerElement.Shape = New LineShape()
    End Sub

    Public Class LineShape
        Inherits ElementShape

        Public Overrides Function CreatePath(ByVal bounds As Rectangle) As GraphicsPath
            Dim path As GraphicsPath = New GraphicsPath()
            Dim start As Point = New Point(bounds.X, bounds.Y)
            Dim [end] As Point = New Point(bounds.X + bounds.Width, bounds.Y)
            path.AddLine(start, [end])
            Return path
        End Function
    End Class