How to: Custom Draw Series

  • 4 minutes to read

This example demonstrates one of several possible ways of using the ChartControl.CustomDrawSeries event. In the sample, the event is used to draw custom legend markers for a series.

A custom legend marker is set to the CustomDrawSeriesEventArgsBase.LegendMarkerImage property. Note that in this case, the CustomDrawSeriesEventArgsBase.DisposeLegendMarkerImage property should be set to true to avoid memory leaks.

To customize options used to draw the series point, cast CustomDrawSeriesEventArgsBase.SeriesDrawOptions to the DrawOptions class descendant that stores draw options of the required series view type.

using CustomDrawingSample.Model;
using DevExpress.XtraCharts;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Linq;

namespace CustomDrawingSample {
    public partial class Form1 : DevExpress.XtraEditors.XtraForm {
        string trackedSeriesName;
        Dictionary<string, Image> photoCache = new Dictionary<string, Image>();

        #region #Constants
        const int borderSize = 5;
        const int scaledPhotoWidth = 48;
        const int scaledPhotoHeight = 51;
        // Width and height of scaled photo with border.
        const int totalWidth = 58;
        const int totalHeight = 61;

        // Rects required to create a custom legend series marker.
        static readonly Rectangle photoRect = new Rectangle(
                borderSize, borderSize,
                scaledPhotoWidth, scaledPhotoHeight);
        static readonly Rectangle totalRect = new Rectangle(
                0, 0,
                totalWidth, totalHeight);
        #endregion

        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {
            using (var context = new NwindDbContext()) {
                InitPhotoCache(context.Employees);
                chart.DataSource = context.Orders.ToList();
            }

            chart.SeriesDataMember = "Employee.FullName";
            chart.SeriesTemplate.ArgumentDataMember = "OrderDate";
            chart.SeriesTemplate.ValueDataMembers.AddRange("Freight");

            XYDiagram diagram = chart.Diagram as XYDiagram;
            if (diagram != null) {
                diagram.AxisX.DateTimeScaleOptions.AggregateFunction = AggregateFunction.Sum;
                diagram.AxisX.DateTimeScaleOptions.MeasureUnit = DateTimeMeasureUnit.Year;
            }

            chart.CustomDrawSeries += OnCustomDrawSeries;
            chart.ObjectHotTracked += OnObjectHotTracked;
        }

        private void OnObjectHotTracked(object sender, HotTrackEventArgs e) {
            trackedSeriesName = e.HitInfo.InSeries ? ((Series)e.HitInfo.Series).Name : null;
        }

        void InitPhotoCache(IEnumerable<Employee> employees) {
            photoCache.Clear();
            foreach (var employee in employees) {
                using (MemoryStream stream = new MemoryStream(employee.Photo)) {
                    if (!photoCache.ContainsKey(employee.FullName))
                        photoCache.Add(employee.FullName, Image.FromStream(stream));
                }
            }
        }

        #region #CustomDrawSeriesImplementation
        private void OnCustomDrawSeries(object sender, CustomDrawSeriesEventArgs e) {
            bool isSelected = e.Series.Name.Equals(trackedSeriesName);
            // Design a series marker image.
            Bitmap image = new Bitmap(totalWidth, totalHeight);
            using (Graphics graphics = Graphics.FromImage(image)) {
                using (var fillBrush = isSelected ? (Brush)new HatchBrush(HatchStyle.DarkDownwardDiagonal,
                                                                          e.LegendDrawOptions.Color,
                                                                          e.LegendDrawOptions.ActualColor2)
                                                  : (Brush)new SolidBrush(e.LegendDrawOptions.Color)) {
                    graphics.FillRectangle(fillBrush, totalRect);
                }
                Image photo;
                if (photoCache.TryGetValue(e.Series.Name, out photo))
                    graphics.DrawImage(photo, photoRect);
            }
            e.LegendMarkerImage = image;
            e.DisposeLegendMarkerImage = true;

            BarDrawOptions options = e.SeriesDrawOptions as BarDrawOptions;
            if (options != null && isSelected) {
                options.FillStyle.FillMode = DevExpress.XtraCharts.FillMode.Hatch;
                ((HatchFillOptions)options.FillStyle.Options).HatchStyle = HatchStyle.DarkDownwardDiagonal;
            }
        }
        #endregion
    }
}
See Also