SAP development trap (06)-There is always a blank item at the bottom of the drop-down list box. How to remove it?

Symptom:

If you use as ListBox on the selection screen or draw a drop-down list box on the screen, a blank item is displayed at the bottom of all options on the business interface, which is annoying.

Solution:

The blank items in the drop-down list box are equivalent to other fields that are not input. Therefore, if you want to remove the blank items, you only need to set them to mandatory.
On the selection screen, use obligatory. For normal screens, the input status of the specified field is required.