Code Sample
output.ListStyle = EntreeListStyles.list_groups;
EntreeListGroup TheGroup = output.AddListGroup();
EntreeDropDownList TheInput = TheGroup.AddFormItem<EntreeDropDownList>("DDList1");
TheInput.Name = "Name";
TheInput.Items.Add("Selected Item", "value");
Example Display
Note: This item style requires the ListStyle to be list_groups
Note: For a ClickActionObject to include the value entered by the user, FormSubmit must be set to true