From Xojo Documentation
| This item has been deprecated since version 2018r4 and should no longer be used.
There is no replacement for this item.
The field in the DataSource that the control is bound to.
Relevant only if the control is used in conjunction with a DataControl to display the contents of fields in a database table. It is assigned the name of a field (String) in the table referenced by the DataControl in the window.
This example specifies the field for the control.