may be it helps:
Private Sub UpdateBlockGraphic(ByVal BlockID As ObjectId)
Using db As Database = Application.DocumentManager.MdiActiveDocument.Database
Using tr As Transaction = db.TransactionManager.StartTransaction
Dim curBlock As BlockReference = CType(tr.GetObject(BlockID, OpenMode.ForWrite), BlockReference)
curBlock.RecordGraphicsModified(True)
tr.Commit()
tr.Dispose()
End Using
End Using
End Sub
or try:
Autodesk.AutoCAD.ApplicationServices.Application.UpdateScreen()