As you may already know, it is required to create a web service to make use of some ASP.NET AJAX Control Toolkit controls. However, you can use static methods of your pages instead, you just have to mark them with the [System.Web.Services.WebMethod] attribute and not set the ServicePath parameter in the ACT controls.

In the example from my article on CascadingDropDown we used a web service for populating the drop-down lists, now we'll use static methods instead, we can just copy-paste the methods from the web service to the code-behind file of the page and remove the ServicePath parameters from the controls.

Extract from Default.aspx.cs

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    [System.Web.Services.WebMethod]
    public static CascadingDropDownNameValue[] GetContinents(string knownCategoryValues, string category)
    {
        CascadingDropDownNameValue[] continents = new CascadingDropDownNameValue[2];
        continents[0] = new CascadingDropDownNameValue("North America", "North America");
        continents[1] = new CascadingDropDownNameValue("Europe", "Europe");
        return continents;
    }
 
Extract from Default.aspx
<%--No ServicePath attribute here--%>
<cc1:CascadingDropDown ID="cddContinent" runat="server" TargetControlID="ddlContinent" 
    Category="continent" ServiceMethod="GetContinents" />

If you don't need to expose the methods consumed by the ACT controls, then you can use static methods instead of web services.