Learn, documentation - ASP.net Awesome

AjaxDropdown

It is declared like this:

<% ParentCategory.AjaxDropdown()
   .Url(Page.Url().Action("GetCategories", "Data")); %>
<awe:Ocon runat="server" ID="ParentCategory" />

The url must return a json of KeyContent collection:

public ActionResult GetCategories()
{
    return Json(Db.Categories.Select(o => new KeyContent(o.Id, o.Name)));
}