AJAX cascading dropdownlist not populating - asp.net

Question

I'm following the tutorial here to try to implement cascading drop down lists using the AJAX toolkit in VS2012, however, I am using MySQL as my database instead. I created a webservice (as the tutorial describes - seen below),
<WebMethod()>
Public Function GetComplex(ByVal knownCategoryValues As String, ByVal category As String) As CascadingDropDownNameValue()
Dim conn As New MySqlConnection("Server=localhost; database=lockout; User ID=root; Pwd=123let?")
conn.Open()
Dim comm As New MySqlCommand("SELECT complex_id, complex_name FROM complex ORDER BY complex_name", conn)
Dim dr As MySqlDataReader = comm.ExecuteReader()
Dim l As New List(Of CascadingDropDownNameValue)
While (dr.Read())
l.Add(New CascadingDropDownNameValue(dr("complex_name").ToString(), dr("complex_id").ToString()))
End While
conn.Close()
Return l.ToArray()
End Function
and I am able to connect to my database and invoke my function. Invoking the function returns the following in my web browser:
<ArrayOfCascadingDropDownNameValue xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://tempuri.org/">
<CascadingDropDownNameValue>
<name>14 Line</name>
<value>1</value>
<isDefaultValue>false</isDefaultValue>
</CascadingDropDownNameValue>
<CascadingDropDownNameValue>
<name>16 Line</name>
<value>2</value>
<isDefaultValue>false</isDefaultValue>
</CascadingDropDownNameValue>
<CascadingDropDownNameValue>
<name>Converting</name>
<value>3</value>
<isDefaultValue>false</isDefaultValue>
</CascadingDropDownNameValue>
<CascadingDropDownNameValue>
<name>F&E</name>
<value>4</value>
<isDefaultValue>false</isDefaultValue>
</CascadingDropDownNameValue>
<CascadingDropDownNameValue>
<name>Water Quality</name>
<value>5</value>
<isDefaultValue>false</isDefaultValue>
</CascadingDropDownNameValue>
</ArrayOfCascadingDropDownNameValue>
I can see that I am generating the necessary array, but for some reason, the array does not appear in my drop down list and I'm not sure why. It looks as though I have covered everything in the tutorial, but I just can't seem to get it to work. Shown below is my .aspx file.
<%# Page Title="LockoutNew" Language="VB" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="LockoutNew.aspx.vb" Inherits="Lockout.LockoutNew" %>
<%# Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="ajaxToolkit" %>
<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="MainContent">
<div>
Complex: <asp:DropDownList ID="ComplexList" runat="server" /><br />
<!-- Machine: <asp:DropDownList ID="MachineList" runat="server" /><br /> -->
</div>
<ajaxToolkit:CascadingDropDown ID="ccd1" runat="server"
ServicePath="lockoutService.asmx" ServiceMethod="GetComplex"
TargetControlID="ComplexList" Category="Complex"
PromptText="Select Complex" />
<!-- <ajaxToolkit:CascadingDropDown ID="ccd2" runat="server"
ServicePath="lockoutService.asmx.vb" ServiceMethod="GetMachine"
TargetControlID="MachineList" ParentControlID="ComplexList"
Category="Machine"
PromptText="Select Machine" /> -->
</asp:Content>
Any help is greatly appreciated...

Answer 1

I had the same exact issue.
The thing is that when building cascading logic u need to know that the first element is different from the rest.
The first in the chain element does not have any parameters to pass to the method !
Thus your method for the first drop down list must contain no parameters :
Public Function GetComplex() As CascadingDropDownNameValue()
Dim conn As New MySqlConnection("Server=localhost; database=lockout; User ID=root; Pwd=123let?")
conn.Open()
Dim comm As New MySqlCommand("SELECT complex_id, complex_name FROM complex ORDER BY complex_name", conn)
Dim dr As MySqlDataReader = comm.ExecuteReader()
Dim l As New List(Of CascadingDropDownNameValue)
While (dr.Read())
l.Add(New CascadingDropDownNameValue(dr("complex_name").ToString(), dr("complex_id").ToString()))
End While
conn.Close()
Return l.ToArray()
End Function