PageMethod not being called what ever. I have defined the Shared Function  in code behind as below

    <system.web.services.webmethod()> _
    <system.web.script.services.scriptmethod()> _
    Public Shared Function GetCity(ByVal StateCode As String) As DataTable
        Dim oDataSet As New DataSet
        Dim oCity As New cCity
        oCity.STATECODE = StateCode
        oDataSet = oCity.GetData
        Return oDataSet.Tables(0)
    End Function

Below is the script which is in the aspx page which I am using to call the codebehind in the server

<script type="text/javascript">
function jsState()
{
  var State = document.getElementById("<%=ddlState.ClientID%>");
  document.getElementById("<%=hfselectedIndexState.ClientID%>").value = document.getElementById("<%=ddlState.ClientID%>").selectedIndex
  if(State.options[State.selectedIndex].value == "-- Select State --")
  {
    document.getElementById("<%=ddlCity.ClientID%>").selectedIndex = 0;
    document.getElementById("<%=ddlCity.ClientID%>").disabled = true;
  }else
  {
    document.getElementById("<%=ddlCity.ClientID%>").disabled = false;
    PageMethods.GetCity(State.options[State.selectedIndex].value,onSuccess_GetCity, onFailed_GetCity);
  }
}
</script>



I did try everything I know . Nothing Worked finally I found that its a silly mistake I forgot to add this line the aspx page

<asp:scriptmanager id="ScriptManager1" runat="server" enablepagemethods="true"></asp:scriptmanager>

Thats it It worked. 

Thanks!
  Murugan