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IF <condition> THEN DO ON ERROR UNDO, THROW:


   CATCH err AS Progress.Lang.Error:
   END CATCH. 
END.

The error handling instruction must be placed above any USING statement.

Event handler

All UI Event handler should have a CATCH for Progress.Lang.Error at the end. If error are not catched here, errors would be thrown to the WAIT-FOR statement which would only display the default error message dialog, which does not look pretty and does not provide further debugging output (other than the stack trace).

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