Release 10.1A: OpenEdge Development:
Programming Interfaces

> ## General conversion features and limitations

> If you set a method input parameter, an event output parameter, or a property to the Unknown value (`?`), Progress 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, Progress 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 Progress data type in your code. For more information on the OpenEdge COM Object Viewer, see Chapter 14, " Using COM Objects in the 4GL." For more information on OCX event procedure templates, see Chapter 16, " ActiveX Control Support."

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