外部导入一个块的问题

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim acDoc As Document = Autodesk..ApplicationServices.Application.DocumentManager.MdiActiveDocument
        Dim destDB As Database = acDoc.Database
        Dim acEditor As Editor = acDoc.Editor
        Dim pPtRes As PromptPointResult
        Dim pPtOpts As PromptPointOptions = New PromptPointOptions("")
        pPtOpts.Message = vbLf & "点:"
        pPtRes = acEditor.GetPoint(pPtOpts)
        Dim InsertPt As Point3d = pPtRes.Value
        If pPtRes.Status = PromptStatus.Cancel Then
            Exit Sub
        End If
        Dim FilePath As String = "D:\2RD\PMDS\PMDS\Resources\PFD.dwg"
        Dim FileName As String = " PFD.dwg"
        Dim BlockName As String = "0920101"
        Dim sourceDb As New Database(True, True)
        sourceDb.ReadDwgFile(FilePath, System.IO.FileShare.Read, True, "")
        Dim blockId As New ObjectIdCollection()
            Using (acDoc.LockDocument)
                Dim sourcetm As Autodesk.AutoCAD.DatabaseServices.TransactionManager = sourceDb.TransactionManager
                Dim desttm As Autodesk.AutoCAD.DatabaseServices.TransactionManager = destDB.TransactionManager
                Dim sourcemyT As Transaction = sourcetm.StartTransaction()
                Dim sourcebt As BlockTable = DirectCast(sourcetm.GetObject(sourceDb.BlockTableId, OpenMode.ForRead, False), BlockTable)
                For Each btrId As ObjectId In sourcebt
                    Dim sourcebtc As BlockTableRecord = DirectCast(sourcetm.GetObject((sourcebt(BlockTableRecord.ModelSpace)), OpenMode.ForRead, False), BlockTableRecord)
                    If sourcebtc.Name = BlockName Then
                        blockId.Add(btrId)
                        Dim mapping As New IdMapping()
                        sourceDb.WblockCloneObjects(blockId, destDB.BlockTableId, mapping, DuplicateRecordCloning.Replace, False)
                        Using destmyT As Transaction = desttm.StartTransaction()
                            Dim destbt As BlockTable = DirectCast(desttm.GetObject(destDB.BlockTableId, OpenMode.ForWrite, True), BlockTable)
                            Dim destbtc As BlockTableRecord = DirectCast(desttm.GetObject((destbt(BlockTableRecord.ModelSpace)), OpenMode.ForRead, False), BlockTableRecord)
                            Dim Block As BlockReference = New BlockReference(InsertPt, destbt(BlockName))
                            Block.ScaleFactors = New Scale3d(1, 1, 1)
                            Block.Rotation = 0
                            Dim ModelSpace As BlockTableRecord = desttm.GetObject(destDB.CurrentSpaceId, OpenMode.ForWrite)
                            ModelSpace.AppendEntity(Block)
                            destmyT.AddNewlyCreatedDBObject(Block, True)
                            destmyT.Commit()
                        End Using
                    ElseIf Not sourcebtc.IsAnonymous AndAlso Not sourcebtc.IsLayout Then
                             End If
                    sourcebtc.Dispose()
                Next
                Me.Close()
            End Using
    End Sub