I think you are going to have to get the COM Interop AcadDocument object - you are currently working with the .NET Document object
Try
acaddoc = DocumentExtension.GetAcadDocument(adoc)
acaddoc.SendCommand(changeViewCommand)
Also possible try the Interop property
acaddoc = AcadDocument.ActiveDocument
I haven’t tested and I’m not sure how Dynamo and .NET may interact