The entitySelection.last( ) method returns a reference to the entity in the last position of the entity selection. 
The result of this method is similar to:
 $entity:=$entitySel[length-1]
If the entity selection is empty, the method returns Null.
 C_OBJECT($entitySelection;$entity)
 $entitySelection:=ds.Emp.query("salary < :1";50000)
 If($entitySelection.length#0)
    $entity:=$entitySelection.last()
 End if