public partial class LegendItems
    {
        static List<SmartPhoneVendor> vendors = new List<SmartPhoneVendor>();
        static Image LegendIconImage = Properties.Resources.usa;
        Series customSeries;
        public LegendItems()
        {
            InitializeComponent();
            vendors = SmartPhoneVendors();       

            // カスタム系列を追加します
            customSeries = new SeriesWithPointLegendItems();
            customSeries.Name = "Sales in USA";
            flexChart1.Series.Add(customSeries);
            flexChart1.Legend.Position = Position.Left;
            flexChart1.ToolTip.Content = "{seriesName}\r\n{value}";
                        
        }
        public class SeriesWithPointLegendItems : Series, ISeries
        {
            object ISeries.GetLegendItemImageSource(int index, ref C1.Chart._Size imageSize)
            {
                {
                    // 元の画像/ロゴはすべて50x50ピクセルです
                    // ここでは、ロゴの周りに5ピクセルのボーダーが追加された新しいイメージに置き換えられます
                    imageSize.Height = 60;
                    imageSize.Width = 60;

                    SmartPhoneVendor vendor = vendors.ElementAt(index);
                    if (LegendIconImage != null && LegendIconImage.Width != 60)
                    {
                        Bitmap bmp = new Bitmap(60, 60);
                        using (SolidBrush sb = new SolidBrush(vendor.Color))
                        {
                            using (Graphics g = Graphics.FromImage(bmp))
                            {
                                Rectangle r = new Rectangle(0, 0, (int)imageSize.Width, (int)imageSize.Height);
                                using (Pen p = new Pen(sb))
                                {
                                    g.DrawRectangle(p, r);
                                }
                                g.FillRectangle(sb, r);

                                Point ci = new Point((int)(0.5 * (imageSize.Width - LegendIconImage.Width)),
                                    (int)(0.5 * (imageSize.Height - LegendIconImage.Height)));
                                g.DrawImage(LegendIconImage, ci);
                            }
                        }
                        LegendIconImage = bmp;
                    }
                    // ロゴビットマップの元のサイズを維持しますが、グラフウィンドウがビットマップを適切に表示するには
    　　　　　　　　　//　小さすぎる場合は、サイズを縮小します
                    Size bounds = this.Chart.ClientSize;
                    double divadj = (bounds.Height > 800) ? 12 : 25;
                    double fracHeight = bounds.Height / divadj;
                    if (fracHeight < imageSize.Height)
                        imageSize.Width = imageSize.Height = fracHeight;
                    return LegendIconImage;
                }
            }
        }
        private static List<SmartPhoneVendor> SmartPhoneVendors()
        {

            vendors.Add(new SmartPhoneVendor()
            {
                Name = "Apple",
                Color = Color.FromArgb(136, 189, 230),
                Sales = 350,
            });
            vendors.Add(new SmartPhoneVendor()
            {
                Name = "LG",
                Color = Color.FromArgb(251, 178, 88),
                Sales = 120,
            });
           
            vendors.Add(new SmartPhoneVendor()
            {
                Name = "Samsung",
                Color = Color.FromArgb(188, 153, 199),
                Sales = 280,
            });
          
            vendors.Add(new SmartPhoneVendor()
            {
                Name = "Xiaomi",
                Color = Color.FromArgb(240, 126, 110),
                Sales = 68,
            });

            return vendors;
        }
        public class SmartPhoneVendor
        {
            public string Name { get; set; }
            public double Sales { get; set; }
            public Color Color { get; set; }
        }
    }