I observed one thing that for drop down list box if we set the attribte 'helpValues' using Model Data Binding. Then the list is showing if the search help assigned to field or data element contains only 2 fields.
For example in SFLIGHT table drop down list box shows for 'CARRID' Field not for 'CONNID' .
The same problem for get_simple_helpvalues2() method also.
Is it right ? or Wrong?