for (int i = 0; i < arrValueNames.Length; i++)
          {
               objGraphics.FillRectangle(new SolidBrush(GetColor(i)), symbolLeg.X, symbolLeg.Y, 20, 10);
               objGraphics.DrawRectangle(Pens.Black, symbolLeg.X, symbolLeg.Y, 20, 10);
               objGraphics.DrawString(arrValueNames[i].ToString(), new Font("宋体", 10), Brushes.Black, descLeg);
               symbolLeg.Y += 15;
               descLeg.Y += 15;
          }