can anyone please tell me why this doesnt work ? I would expect that when i start typing, the data retrieval method on my controller should be called, but its not

@Html.Infragistics().Combo().ID("comboOrganisation").DataSourceUrl(Url.Action("AutoComplete", "User")).ValueKey("User_Org").TextKey("User_Org").Width("300px").AutoComplete(true).Render()

[ActionName("AutoComplete")]
public async Task<ActionResult> ComboData(string search)
{
GetOrganisationRequest request = new GetOrganisationRequest(search);
JsonResult result = new JsonResult();
result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;

var organisations = await this._organisationService.OrganisationAutoCompleteAsync(request);
result.Data = organisations;

result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
return result;
}