ASP.NET DropDownList with OptionGroup support

<br />
if (item.Attributes[OPTGROUPATTR] == null && !optionGroups.ContainsKey(keyString))<br />
{<br />
  if (blGroupOpen)<br />
  {<br />
    RenderOptionGroupEndTag(writer);<br />
    blGroupOpen = false;<br />
    renderedOptionGroupsClosed.Add(currentOptionGroup);<br />
  }<br />
  RenderListItem(item, writer);<br />
}<br />
else<br />
{<br />
  if (item.Attributes[OPTGROUPATTR] != null)<br />
    currentOptionGroup = item.Attributes[OPTGROUPATTR];<br />
  else<br />
  {<br />
    while (renderedOptionGroupsClosed.Contains(optionGroups[keyString]))<br />
      keyString += "*";<br />
    currentOptionGroup = optionGroups[keyString];<br />
  }<br />
.<br />
.<br />
.<br />
      RenderOptionGroupBeginTag(currentOptionGroup, writer);<br />
      blGroupOpen = true;<br />
.<br />
.<br />
.<br />
if (blGroupOpen)<br />
{<br />
  RenderOptionGroupEndTag(writer);<br />
  renderedOptionGroupsClosed.Add(currentOptionGroup);<br />
}<br />

<br />
protected override object SaveAdapterViewState()<br />
{<br />
  DropDownList list = this.Control as DropDownList;<br />
  foreach (ListItem item in list.Items)<br />
  {<br />
    if (item.Attributes[OPTGROUPATTR] != null)<br />
    {<br />
      string currentOptionGroup = item.Attributes[OPTGROUPATTR];<br />
      string keyString = item.Value + item.Text;<br />
      while (optionGroups.ContainsKey(keyString))<br />
        keyString += "*";<br />
      optionGroups[keyString] = currentOptionGroup;<br />
    }<br />
  }<br />
  return optionGroups;<br />
}<br />

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;
}

protected override void LoadAdapterViewState(object state)
{

    optionGroups = state as Dictionary<string, string>;
}

select optgroup {<br />
	font-style: normal;<br />
}

<br />
    protected void Page_Load(object sender, EventArgs e)<br />
    {<br />
        if (!IsPostBack)<br />
        {<br />
PopulateListWithValues();<br />
}<br />
}<br />

Imports System.Web.UI
Imports System.Web.UI.WebControls

	Public Class ComboBox
		Inherits DropDownList

		Private Const m_optionGroupAttribute As String = "OptionGroup"
		Private Const m_tagOptionGroup As String = "optgroup"
		Private Const m_attributeLabel As String = "label"
		Private m_viewstates As Object()

		Protected Overrides Sub RenderContents(ByVal writer As HtmlTextWriter)
			If (Not Page Is Nothing) Then
				Dim l_list As DropDownList = CType(Me, DropDownList)
				Dim l_currentOptionGroup As String
				Dim l_renderedOptionGroups As New ArrayList()

				For Each l_item As ListItem In l_list.Items
					Page.ClientScript.RegisterForEventValidation(l_list.UniqueID, l_item.Value)

					If l_item.Attributes(m_optionGroupAttribute) Is Nothing Then
						RenderListItem(l_item, writer)
					Else
						l_currentOptionGroup = l_item.Attributes(m_optionGroupAttribute)

						If (l_renderedOptionGroups.Contains(l_currentOptionGroup)) Then
							RenderListItem(l_item, writer)
						Else
							If (l_renderedOptionGroups.Count > 0) Then
								RenderOptionGroupEndTag(writer)
							End If
							RenderOptionGroupBeginTag(l_currentOptionGroup, writer)
							l_renderedOptionGroups.Add(l_currentOptionGroup)
							RenderListItem(l_item, writer)
						End If
					End If
				Next

				If (l_renderedOptionGroups.Count > 0) Then
					RenderOptionGroupEndTag(writer)
				End If
			Else
				MyBase.RenderContents(writer)
			End If
		End Sub

		Private Sub RenderOptionGroupBeginTag(ByVal name As String, ByVal writer As HtmlTextWriter)
			writer.AddAttribute(m_attributeLabel, name)
			writer.RenderBeginTag(m_tagOptionGroup)
		End Sub

		Private Sub RenderOptionGroupEndTag(ByVal writer As HtmlTextWriter)
			writer.RenderEndTag()
		End Sub

		Private Sub RenderListItem(ByVal item As ListItem, ByVal writer As HtmlTextWriter)
			For Each key As String In item.Attributes.Keys
				If (key <> m_optionGroupAttribute) Then
					writer.AddAttribute(key, item.Attributes(key))
				End If
			Next

			writer.AddAttribute(HtmlTextWriterAttribute.Value, item.Value, True)

			If (item.Selected) Then
				writer.AddAttribute(HtmlTextWriterAttribute.Selected, "selected")
			End If

			writer.RenderBeginTag(HtmlTextWriterTag.Option)
			writer.WriteEncodedText(item.Text)
			writer.RenderEndTag()
		End Sub

		Protected Overrides Function SaveViewState() As Object
			If (Not Page Is Nothing) Then
				Dim l_list As DropDownList = CType(Me, DropDownList)
				Dim l_viewState(l_list.Items.Count) As Object ' Note: Count + 1 caused eventvalidation errors.

				Dim i As Integer = 0
				For Each item As ListItem In l_list.Items

					l_viewState(i) = item.Attributes(m_optionGroupAttribute)
					i += 1
				Next

				l_viewState(i) = MyBase.SaveViewState()
				Return l_viewState
			Else
				Return MyBase.SaveViewState()
			End If
		End Function

		Protected Overrides Sub LoadViewState(ByVal state As Object)
			If (Not Page Is Nothing) Then
				m_viewstates = CType(state, Object())
				MyBase.LoadViewState(m_viewstates(m_viewstates.Length - 1))
			Else
				MyBase.LoadViewState(state)
			End If
		End Sub

		Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs)
			If (Not Page Is Nothing) Then
				If (Not m_viewstates Is Nothing AndAlso m_viewstates.Length > 1) Then
					Dim l_list As DropDownList = CType(Me, DropDownList)
					If (Page.EnableEventValidation) Then
						If (m_viewstates.Length <> l_list.Items.Count + 1) Then
							Throw New ViewStateException()
						End If
					End If

					Dim l_max As Integer = m_viewstates.Length
					If (l_list.Items.Count < l_max) Then
						l_max = l_list.Items.Count
					End If

					For i As Integer = 0 To l_max - 1
						l_list.Items(i).Attributes(m_optionGroupAttribute) = CStr(m_viewstates(i))
					Next
				End If
			End If

			MyBase.OnPreRender(e)
		End Sub
	End Class