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Programming Interfaces
COM Object Data Type Mapping : Data type conversion strategy : General conversion features and limitations

General conversion features and limitations

If you set a method input parameter, an event output parameter, or a property to the Unknown value (?), ABL converts this value to the COM Null value. Similarly, if a COM object returns a Null value in a method output parameter, an event input parameter, or a property, ABL converts this value to the Unknown value (?).
When the OpenEdge COM Object Viewer suggests the syntax for a property or method reference or the AppBuilder generates a template for an OCX event procedure, it indicates any method parameter or property with an undetermined data type using the place holder, anytype. You must replace anytype with a valid ABL data type in your code. For more information on the OpenEdge COM Object Viewer, see Using COM Objects in ABL. For more information on OCX event procedure templates, see ActiveX Control Support.