The type or namespace "series collection" could not be found

<pre>using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Drawing.Drawing2D;

namespace dotnetpro
{
    public partial class sample1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Chart.TitleBox.Label.Text = "Student Progress";
            Chart.Width = 750;
            Chart.Height = 550;
            SeriesCollection mySC = Calculate();
            Chart.XAxis.Label.Text = "Marks";
            Chart.YAxis.Label.Text = "No of Students";
            Chart.SeriesCollection.Add(Calculate());
            Chart.DefaultSeries.DefaultElement.URL = "JavaScript: myAlert(\'Clicked on element %Name in series %SeriesName \')";
            Chart.TitleBox.Position = TitleBoxPosition.Full;
            Chart.TitleBox.Label.Font = new Font("TimesRoman", 10, FontStyle.Bold | FontStyle.Italic);
            Chart.TitleBox.Label.Alignment = StringAlignment.Center;
            Chart.TitleBox.Label.Color = Color.DarkBlue;
            Chart.TitleBox.Background.Color = Color.FromArgb(225, 122, 212);
            Chart.TitleBox.Padding = 7;
            Chart.LegendBox.DefaultEntry.LabelStyle.Font = new Font("Arial", 10, FontStyle.Italic);
            Chart.LegendBox.Line.Color = Color.FromArgb(56, 66, 177);
            Chart.LegendBox.Line.Width = 2;
            Chart.LegendBox.Background = new Background(Color.FromArgb(165, 174, 255), Color.FromArgb(233, 235, 240), 45);
            Chart.LegendBox.Orientation = dotnetCHARTING.Orientation.Bottom;
        }
       SeriesCollection Calculate()
        {
            SeriesCollection SC = new SeriesCollection();
            Random myR = new Random(1);
            for (int a = 0; a < 4; a++)
            {
                Series s = new Series();
                s.Name = "Series " + a.ToString();
                for (int b = 0; b < 1; b++)
                {
                    Element e = new Element();
                    e.Name = "Element " + b.ToString();
                    e.YValue = myR.Next(50);
                    s.Elements.Add(e);
                }

                SC.Add(s);
            }
            SC[0].Element.Color = Color.FromArgb(49, 255, 49);
            SC[0].Elements[0].Name = "English";
            SC[0].LegendEntry.Value = "13";
            SC[0].LegendEntry.Name = "Between 10-15";

            SC[1].Element.Color = Color.FromArgb(255, 255, 0);
            SC[1].Elements[0].Name = "Maths";
            SC[1].LegendEntry.Value = "32";
            SC[1].LegendEntry.Name = "Between 10-40";

            SC[2].Element.Color = Color.FromArgb(255, 99, 49);
            SC[2].Elements[0].Name = "Science";
            SC[2].LegendEntry.Value = "6";
            SC[2].LegendEntry.Name = "Between 0-10";

            SC[3].Element.Color = Color.FromArgb(0, 156, 255);
            SC[3].Elements[0].Name = "Computer";
            SC[3].LegendEntry.Value = "18";
            SC[3].LegendEntry.Name = "Between 15-30";
            return SC;
        }


    }
}