ASP.NET DropDownList with OptionGroup support

public void fillCountry(DropDownList drp){
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString = ""; //add your connection string
    string sql = "select country, province from countryList order by country, province";
    conn.Open();
    SqlCommand cmd=new SqlCommand(sql, conn);
    SqlDataReader dr = cmd.ExecuteReader();
    string grph = "";   //group header
    while (dr.Read())
    {
       ListItem drpg;  //dropdown group
       ListItem drpi;  //dropdown item
       if (grph != dr.GetSqlString(0).ToString())
       {
           //adding the country - group
           drpg = new ListItem(dr.GetSqlString(0).ToString(), dr.GetSqlString(0).ToString());  
           grph = dr.GetSqlString(0).ToString();
           drp.Items.Add(drpg);
           drpg.Attributes.Add("disabled", "disabled");
           drpg.Attributes.Add("style", "background-color:lightblue;");
       }
       //adding the province - items
       drpi=new ListItem(dr.GetSqlString(1).ToString(), dr.GetSqlString(1).ToString());                  
       drp.Items.Add(drpi);
       grph = dr.GetSqlString(0).ToString();
     }
     conn.Close();
}

ddlCountry.DataSource = CountryCollection;
           ddlCountry.DataBind();

<browsers>
  <browser refID="Default">
    <controlAdapters>
      <adapter controlType="System.Web.UI.WebControls.AdRotator"
				   adapterType="My.Namespace.Project.Code.Adapters.AdRotatorAdaptor" />
    </controlAdapters>
  </browser>
</browsers>

ListItem item6 = new ListItem("Allosaurus", "6");
item6.Attributes["OptionGroup"] = "Dinosaurs";

ListItem item7 = new ListItem("Trex", "7");

   Protected Overloads Overrides Sub RenderContents(ByVal writer As HtmlTextWriter)
        Dim list As DropDownList = TryCast(Me.Control, DropDownList)
 
        Dim currentOptionGroup As String
        Dim renderedOptionGroups As New List(Of String)()
 
        Dim tagClosed As Boolean = True
        For Each item As ListItem In list.Items
            If item.Attributes("OptionGroup") Is Nothing OrElse item.Attributes("OptionGroup") = "" Then
                If Not tagClosed Then RenderOptionGroupEndTag(writer) : tagClosed = True
                RenderListItem(item, writer)
            Else
                currentOptionGroup = item.Attributes("OptionGroup")
 
                If renderedOptionGroups.Contains(currentOptionGroup) Then
                    RenderListItem(item, writer)
                Else
                    If tagClosed = False Then
                        RenderOptionGroupEndTag(writer)
                        tagClosed = True
                    End If
 
                    RenderOptionGroupBeginTag(currentOptionGroup, writer)
                    renderedOptionGroups.Add(currentOptionGroup)
 
                    RenderListItem(item, writer)
                    tagClosed = False
                End If
            End If
        Next
 
        If tagClosed = False Then
            RenderOptionGroupEndTag(writer)
        End If
    End Sub

    public class DropDownListAdapter : System.Web.UI.WebControls.Adapters.WebControlAdapter {
 
        public static readonly string OPTGROUPATTR = "OptionGroup";
 
        Dictionary<string, string> optionGroups = new Dictionary<string, string>();
 
        protected override void RenderContents(HtmlTextWriter writer) {
            DropDownList list = this.Control as DropDownList;
 
            string currentOptionGroup;
            List<string> renderedOptionGroups = new List<string>();
 
            foreach(ListItem item in list.Items) {
                string keyString = item.Value + item.Text;
                if(item.Attributes[OPTGROUPATTR] == null && !optionGroups.ContainsKey(keyString)) {
                    RenderListItem(item, writer);
                } else {
                    if (item.Attributes[OPTGROUPATTR] != null)
                        currentOptionGroup = item.Attributes[OPTGROUPATTR];
                    else
                    {
                        currentOptionGroup = optionGroups[keyString];
                    }
 
                    if(renderedOptionGroups.Contains(currentOptionGroup)) {
                        RenderListItem(item, writer);
                    } else {
                        if(renderedOptionGroups.Count > 0) {
                            RenderOptionGroupEndTag(writer);
                        }
 
                        RenderOptionGroupBeginTag(currentOptionGroup, writer);
                        renderedOptionGroups.Add(currentOptionGroup);
 
                        RenderListItem(item, writer);
                    }
                }
            }
 
            if(renderedOptionGroups.Count > 0) {
                RenderOptionGroupEndTag(writer);
            }
        }
 
        private void RenderOptionGroupBeginTag(string name, HtmlTextWriter writer) {
            writer.WriteBeginTag("optgroup");
            writer.WriteAttribute("label", name);
            writer.Write(HtmlTextWriter.TagRightChar);
            writer.WriteLine();
        }
 
        private void RenderOptionGroupEndTag(HtmlTextWriter writer) {
            writer.WriteEndTag("optgroup");
            writer.WriteLine();
        }
 
        private void RenderListItem(ListItem item, HtmlTextWriter writer) {
 
            this.Page.ClientScript.RegisterForEventValidation(this.Control.UniqueID, item.Value);
 
            writer.WriteBeginTag("option");
            writer.WriteAttribute("value", item.Value, true);
 
            if(item.Selected) {
                writer.WriteAttribute("selected", "selected", false);
            }
 
            foreach(string key in item.Attributes.Keys) {
                writer.WriteAttribute(key, item.Attributes[key]);
            }
 
            writer.Write(HtmlTextWriter.TagRightChar);
            HttpUtility.HtmlEncode(item.Text, writer);
            writer.WriteEndTag("option");
            writer.WriteLine();
        }
 
        //
        // Summary:
        //     Saves view state information for the control adapter.
        //
        // Returns:
        //     An System.Object that contains the adapter view state information as a System.Web.UI.StateBag.
        protected override object SaveAdapterViewState()
        {
            DropDownList list = this.Control as DropDownList;
            string currentOptionGroup;
            string keyString;
 
            foreach (ListItem item in list.Items)
            {
                if (item.Attributes[OPTGROUPATTR] != null)
                {
                    currentOptionGroup = item.Attributes[OPTGROUPATTR];
                    keyString = item.Value + item.Text;
                    optionGroups[keyString] = currentOptionGroup;
                }
            }
 

            return optionGroups;
        }
 

        //
        // Summary:
        //     Loads adapter view state information that was saved by System.Web.UI.Adapters.ControlAdapter.SaveAdapterViewState()
        //     during a previous request to the page where the control associated with this
        //     control adapter resides.
        //
        // Parameters:
        //   state:
        //     An System.Object that contains the adapter view state information as a System.Web.UI.StateBag.
        protected override void LoadAdapterViewState(object state)
        {
 
            optionGroups = state as Dictionary<string, string>;    
        }
 
    }