.IsDynamicBlock 返回 false ？

Function main()
...
Using Transaction tr = db.TransactionManager.StartTransaction()
Dim DbObjectCollection blocks = get_blocks(db, tr)
sort_blocks(blocks)
...
End Using
End Function
Function get_Blocks(db As Database, tr as Transaction) As DbObjectCollection
If tr == null Then throw new ArgumentNullException( "Function called outside the scope of transaction" )
...get blocks
End Function

Sub Main()
        ' Get the current document and database
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database
        ' Lock the document
        Using acLckDoc As DocumentLock = acDoc.LockDocument()
            ' Start a transaction
            Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
                
                Call function1()
                dim obj as DbObject = function2()
                If TypeOf (obj) Is BlockReference Then
                      Call function3(obj)
                end if
                ' Save the changes
                acTrans.Commit()
            End Using ' Transaction
        End Using ' Lock
End Sub
Function method1()
        ' Get the current document and database
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database
        Dim acTrans As Transaction = db.TransactionManager.TopTransaction
        Dim blkTable As BlockTable = acTrans.GetObject(acCurDb.BlockTableId, OpenMode.ForRead)
        If blkTable.Has(_blockName) Then
            ......
        End If
End Function
Function method2() as DBObject
        ' Get the current document and database
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database
        Dim acTrans As Transaction = db.TransactionManager.TopTransaction
        Dim pPtOpts As PromptEntityOptions = New PromptEntityOptions("")
        ' Prompt for the start point
        pPtOpts.Message = vbLf & _prompt
        pPtOpts.AllowNone = False
        Dim pPtRes As PromptEntityResult = acDoc.Editor.GetEntity(pPtOpts)
        ' Exit if the user presses ESC or cancels the command
        If pPtRes.Status = PromptStatus.Cancel Then Return Nothing
        Return acTrans.GetObject(pPtRes.ObjectId, OpenMode.ForRead)
End Function
sub method3(_blkRef as BlockReference)
       ' Get the current document and database
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database
        Dim acTrans As Transaction = db.TransactionManager.TopTransaction
        Dim attCol As AttributeCollection = _blkRef.AttributeCollection
        For Each attId As ObjectId In attCol
             Dim attRef As AttributeReference = DirectCast(acTrans.GetObject(attId, OpenMode.ForWrite), AttributeReference)
             Dim recievedValue As String = get_AttVal(attRef.Tag, _attVals)
             If Not String.IsNullOrEmpty(recievedValue) Then attRef.TextString = recievedValue
        Next
End sub