database.insert 是不是有问题

把一个database里的某个 layout 复制到当前图形里，简化代码如下（代码无意义，只为表达问题）：

    <CommandMethod("test", CommandFlags.Modal)>
    Public Sub Test2()
        Dim db As Database = Application.DocumentManager.MdiActiveDocument.Database
        Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
        Dim tm As DatabaseServices.TransactionManager = db.TransactionManager
        Dim myT As Transaction = tm.StartTransaction()
        Try
            Using oDbSource As New Database(True, False)
                Dim oLayoutsSource As DBDictionary = CType(tm.GetObject(oDbSource.LayoutDictionaryId, OpenMode.ForRead), DBDictionary)
                Dim oLayoutFrom As Layout = CType(tm.GetObject(oLayoutsSource.GetAt("布局1"), OpenMode.ForRead), Layout)
                Dim oBtrFrom As BlockTableRecord = CType(tm.GetObject(oLayoutFrom.BlockTableRecordId, OpenMode.ForRead), BlockTableRecord)

                Dim idNewBtr As ObjectId = db.Insert(oBtrFrom.Name, oBtrFrom.Name, oDbSource, True)
                Dim oNewBtr As BlockTableRecord = CType(tm.GetObject(idNewBtr, OpenMode.ForRead), BlockTableRecord)
                Dim idNewLayout As ObjectId = oNewBtr.LayoutId
                Dim oNewLayout As Layout = CType(tm.GetObject(idNewLayout, OpenMode.ForRead), Layout)
                Dim oLM As LayoutManager = LayoutManager.Current
                oLM.CurrentLayout = oNewLayout.LayoutName

            End Using
        Catch ex As Exception
            ed.WriteMessage(ex.Message)
        Finally
            myT.Commit()

        End Try
    End Sub

其中 Dim idNewBtr As ObjectId = db.Insert(oBtrFrom.Name, oBtrFrom.Name, oDbSource, True) 那一行，从oDbSource中把“布局1”的内容复制到本图中，然后建立layout，并把新的layout设置为当前布局。

这段代码在ACAD中可以正常运行。

但中望会产生非法内存读写错误并闪退：“System.AccessViolationException:“尝试读取或写入受保护的内存。这通常指示其他内存已损坏。”

试着把myT.Commit移到End Using前面，就能产生正常结果。但是在实际程序中，这只是一个小部分，不可能在这里commit。

这是不是说明database.insert那里有点问题？按说把布局上的东西复制到本图中之后，对原oDbSource就没有依赖了，oDbSource被End Using，不应该影响后续的commit。

把一个database里的layout复制到本图中，有什么绕过去的建议？