DropDownList with OptionGroup

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using OptionDropDownList;

namespace TestWebApplication
{
  public partial class Default : System.Web.UI.Page
  {
    /// <summary>
    /// 
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void Page_Load(object sender, EventArgs e)
    {
      this.DropDownList1.DataTextField = "letter";
      this.DropDownList1.DataValueField = "id";
      this.DropDownList1.DataSource = this.CreateDataSource();
      this.DropDownList1.DataBind();
      this.OptionGroupSelect1.DataTextField = "letter";
      this.OptionGroupSelect1.DataValueField = "id";
      this.OptionGroupSelect1.OptionGroupField = "letters";
      this.OptionGroupSelect1.DataSource = this.CreateDataSource();
      this.OptionGroupSelect1.DataBind();


      this.DropDownList2.DataTextField = "letter";
      this.DropDownList2.DataValueField = "id";
      this.DropDownList2.DataSource = this.CreateDataSource();
      this.DropDownList2.DataBind();
      this.OptionGroupSelect2.DataTextField = "letter";
      this.OptionGroupSelect2.DataValueField = "id";
      this.OptionGroupSelect2.OptionGroupField = "letters";
      this.OptionGroupSelect2.DataSource = this.CreateDataSource();
      this.OptionGroupSelect2.DataBind();


      this.DropDownList3.DataTextField = "letter";
      this.DropDownList3.DataValueField = "id";
      this.DropDownList3.DataSource = this.CreateDataSource();
      this.DropDownList3.DataBind();
      this.OptionGroupSelect3.DataTextField = "letter";
      this.OptionGroupSelect3.DataValueField = "id";
      this.OptionGroupSelect3.OptionGroupField = "letters";
      this.OptionGroupSelect3.DataSource = this.CreateDataSource();
      this.OptionGroupSelect3.DataBind();


      if (!this.IsPostBack)
      {
        this.DropDownList5.DataTextField = "letter";
        this.DropDownList5.DataValueField = "id";
        this.DropDownList5.DataSource = this.CreateDataSource();
        this.DropDownList5.DataBind();
      }
      this.OptionGroupSelect5.DataTextField = "letter";
      this.OptionGroupSelect5.DataValueField = "id";
      this.OptionGroupSelect5.OptionGroupField = "letters";
      this.OptionGroupSelect5.DataSource = this.CreateDataSource();
      this.OptionGroupSelect5.DataBind();
    }

    /// <summary>
    /// 
    /// </summary>
    /// <returns></returns>
    private ICollection CreateDataSource()
    {
      DataTable dt = new DataTable();
      DataRow dr;

      dt.Columns.Add(new DataColumn("id", typeof(String)));
      dt.Columns.Add(new DataColumn("letter", typeof(String)));
      dt.Columns.Add(new DataColumn("letters", typeof(String)));

      dr = dt.NewRow();
      dr[0] = "A";
      dr[1] = "letter A";
      dr[2] = "letters";
      dt.Rows.Add(dr);

      dr = dt.NewRow();
      dr[0] = "B";
      dr[1] = "letter B";
      dr[2] = "letters";
      dt.Rows.Add(dr);

      dr = dt.NewRow();
      dr[0] = "C";
      dr[1] = "letter C";
      dr[2] = "letters";
      dt.Rows.Add(dr);

      dr = dt.NewRow();
      dr[0] = "D";
      dr[1] = "letter D";
      dr[2] = "letters";
      dt.Rows.Add(dr);

      dr = dt.NewRow();
      dr[0] = "E";
      dr[1] = "letter E";
      dr[2] = "letters";
      dt.Rows.Add(dr);

      DataView dv = new DataView(dt);
      return dv;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void OptionGroupSelect_ValueChanged(object sender, EventArgs e)
    {
      this.textbox1.Text = "selected --> " + ((OptionGroupSelect)sender).SelectedItem.Text;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void DropDownList_SelectedIndexChanged(object sender, EventArgs e)
    {
      this.textbox1.Text = "selected --> " + ((DropDownList)sender).SelectedItem.Text;
    }
  }
}