Document.ClassID Property (Visio)
Returns the class ID string of the container application in which the document is embedded. Read-only.
If the class ID of the container application in which the document is embedded cannot be retrieved, the ClassID property raises an exception. If the document is not embedded in a container, the ClassID property returns an empty string.
ClassID returns a string of the form:
This string identifies the application that contains the document. It might, for example, identify the document's container as a Microsoft Excel object.