You can check the block's PaperOrientation enum value which is read-only but use the DBObject.SetPaperOrientation Method which a BlockTableRecord is a DBObject
Here is a example showing both members for changing "match orientation to layout" to TRUE for a block named 'C'
You might need to Regen for changes to show up
<CommandMethod("ChangePaperOreintation")> _
Public Sub ChangePaperOreintation()
Dim doc As Document = Application.DocumentManager.MdiActiveDocument
Dim db As Database = doc.Database
Dim ed As Editor = doc.Editor
Using trx As Transaction = db.TransactionManager.StartTransaction()
Dim bt As BlockTable = trx.GetObject(db.BlockTableId, OpenMode.ForRead)
If bt.Has("C") Then
Dim btr As BlockTableRecord = trx.GetObject(bt("C"), OpenMode.ForRead)
If btr.PaperOrientation = PaperOrientationStates.False Then
btr.UpgradeOpen()
btr.SetPaperOrientation(True)
End If
End If
trx.Commit()
End Using
End Sub