dato il seguente web service:
codice:
Imports System.Web   
Imports System.Web.Services   
Imports System.Web.Services.Protocols   
Imports System.Data.OleDb   
Imports System.Data   
Imports AjaxControlToolkit   
Imports System.Collections.Generic   
  
  
' To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.   
' <System.Web.Script.Services.ScriptService()> _   
<WebService(Namespace:="http://tempuri.org/")> _   
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _   
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _   
Public Class WebService   
    Inherits System.Web.Services.WebService   
  
  
    Dim Conoledb As New OleDbConnection   
  
    Public codProvincia As String   
    Public provincia As String   
    Public CodiceProvincia As String   
    Public RcodRegione As Integer   
    Public descRegione As String   
  
    Public Function ListaProvince() As CascadingDropDownNameValue()   
        Dim strConnection As String = ConfigurationManager.AppSettings("ConnectionSting").ToString   
        Dim DT As New DataTable("Tabella")   
        StrSql = "SELECT * FROM province WHERE 1=1 "   
  
        If RcodRegione <> "" Then StrSql = StrSql & " AND RcodRegione=" & RcodRegione   
        'filtro per il tipo di cliente ricercato (per le liste)   
  
        Dim DTA As New OleDbDataAdapter(StrSql, Conoledb)   
        DTA.Fill(DT)   
        DTA = Nothing   
        Dim myPlayers As New List(Of CascadingDropDownNameValue)   
  
        For i = 0 To DT.Rows.Count - 1   
            Dim strPlayerName As String = DT.Rows(i)("Provincia").ToString   
            Dim strPlayerId As String = DT.Rows(i)("codProvincia").ToString   
  
            myPlayers.Add(New CascadingDropDownNameValue(strPlayerName, strPlayerId))   
        Next   
  
        Return myPlayers.ToArray   
  
    End Function   
End Class
e la pagina aspx

codice:

<asp:DropDownList ID="DropDownList1" runat="server" Width="182px">   
                   </asp:DropDownList>
   
                    <asp:DropDownList ID="DropDownList2" runat="server" Width="182px">   
                   </asp:DropDownList>
   
              
                       
                     <ajaxToolkit:CascadingDropDown   
                       ID="CascadingDropDown2"   
                       runat="server"   
                       Category="province"   
                       PromptText="Select a manufacturer"   
                       ServicePath="WebService.asmx"   
                       ServiceMethod="ListaProvince" TargetControlID="DropDownList1" />    
                          
                            
                     <ajaxToolkit:CascadingDropDown   
                       ID="ddlMake"   
                       ParentControlID="DropDownList1"   
                       runat="server"   
                       Category="province"   
                       PromptText="Select a manufacturer"   
                       ServicePath="WebService.asmx"   
                       ServiceMethod="ListaProvince" TargetControlID="DropDownList2"/>
]
ho seguito l'esempio da
http://programming.top54u.com/post/A...-Database.aspx

la prima dropdown mi compare a video, ma come primo elelemtno mi compare "error 500"
da cosa puo dipendere?, cosa ho sbagliato qui?

ho qualche dubbio su category, sarebbe il gat del dropdown...ma ho provato a mettere la tabella dove vado a selezionare..ma sempre lo stesso errore