Error handling for ABL-extended .NET classes

As noted previously, an ABL method that overrides a .NET method, or that implements a method defined in a .NET interface, can be called from the .NET context. Similarly, an ABL property that implements a property defined in a .NET interface can be accessed from the .NET context. When you raise ERROR from within such an ABL method or property accessor that is invoked from the .NET context, and the specified ABL error options raise the error condition out of the method or accessor block, ABL returns a .NET System.ApplicationException to the caller.

If you raise the error condition by executing a RETURN ERROR with the optional error string, the Message property of the System.ApplicationException is available to the ABL context using the RETURN-VALUE function. If you raise the error condition by executing a RETURN ERROR with an optional ABL error object, or by executing an UNDO, THROW of the ABL error object, the Message property of the System.ApplicationException includes any messages from the ABL error object.

Note that ABL responds to errors raised from ABL handlers that you subscribe to ABL-inherited .NET events in exactly the same way as errors raised from ABL handlers of .NET instance or static events published by pure .NET classes. For more information, see Handling .NET exceptions raised during display of a .NETform.