<asp:HyperLink ID="lnkHome" runat="server" 
   NavigateUrl="~/default.aspx" 
   CssClass='<%#GetCss(lnkHome) %>'>
   Home
</asp:HyperLink>

Protected Function GetCss(ByVal lnk As HyperLink) As String

<ul id="UlHomeSubMenu" runat="server" 
   visible='<%# GetUlSubVisible(lnkHome, UlHomeSubMenu) %>'>
     ... Untermüpunkte ....

Protected Function GetCss(ByVal lnk As HyperLink) As String
	Dim linkUrl As String = lnk.NavigateUrl
	Dim pageUrl As String = Request.AppRelativeCurrentExecutionFilePath
	If linkUrl.Equals(pageUrl, StringComparison.OrdinalIgnoreCase) Then
		Return "selected"
	Else
		Return ""
	End If
End Function
Protected Function GetUlSubVisible(ByVal topLink As HyperLink, ByVal ul As _
  HtmlGenericControl) As Boolean
	Dim pageUrl As String = Request.AppRelativeCurrentExecutionFilePath
	Dim linkUrl As String = topLink.NavigateUrl
	If linkUrl.Equals(pageUrl, StringComparison.OrdinalIgnoreCase) Then
		Return True
	End If
 
	For Each ctrl As Control In ul.Controls
		Dim lnk As HyperLink = TryCast(ctrl, HyperLink)
		If lnk Is Nothing Then Continue For
		linkUrl = lnk.NavigateUrl
		If linkUrl.Equals(pageUrl, StringComparison.OrdinalIgnoreCase) Then
			Return True
		End If
	Next
	Return False
End Function