protected void setupDisplayDataCascadingDropDown() { // now, let's set up the cascading CascadingPair pair = new CascadingPair() { ParentDropDownID = ddlDataType.ID, ChildDropDownID = ddlDisplayType.ID }; // and let's apply the dependencies properly foreach (ListItem dataType in ddlDataType.Items) { var dependentDisplayTypes = FieldMappings.GetDependentDisplayTypesFor(dataType.Value.ToEnum <FieldDataType>()); ParentDropDownValue v = new ParentDropDownValue() { Value = dataType.Value }; foreach (var dependentDisplayType in dependentDisplayTypes) { v.ChildDropDownValues.Add(new ChildDropDownValue() { Value = dependentDisplayType.ToString() }); } pair.ParentDropDownValues.Add(v); } CascadingDropDownManager1.CascadingPairs.Add(pair); }