Microsoft Visual Studio – ASP.Net Wrox Professional ASP.NET: In C# and vb – Chapter 19 CascadingDropDown Sample Causing Method Error 500

When debugging, the actual error states:

Unable to cast object of type ‘System.Object[]’ to type ‘AjaxControlToolkit.CascadingDropDownNameValue[]’.

After doing much research on this issue, it appears everyone’s resolution was to ensure that you included the ‘<WebMethod(), System.Web.Script.Services.ScriptMethod()> _’ above the public …