id.getobject失效了吗？ 出致命错误！？

zoomify

下面的代码
        <CommandMethod("ShowEntType")>
        Public Shared Sub Crotate()
            Dim db As Database = HostApplicationServices.WorkingDatabase
            Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
            ed = Application.DocumentManager.MdiActiveDocument.Editor
            ed.WriteMessage(vbLf & "选择实体: ")
            Dim res As PromptSelectionResult = ed.GetSelection()
            Dim SS As SelectionSet = res.Value
            For Each theid As ObjectId In SS.GetObjectIds
               Dim ent As Entity = CType(theid.GetObject(OpenMode.ForWrite), Entity)
               ed.WriteMessage(ent.GetType.ToString)
            Next
        End Sub

会在Dim ent As Entity = CType(theid.GetObject(OpenMode.ForWrite), Entity) 这里出致命错误，只有用
    Dim db As Database
            Dim tm As Transaction
            db = HostApplicationServices.WorkingDatabase
            tm = db.TransactionManager.StartTransaction()

            '  Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor

            '构建用于移动实体的矩阵
            Dim vector As Vector3d = sourcePt.GetVectorTo(targetPt)
            Dim mt As Matrix3d = Matrix3d.Displacement(vector)

            '以写的方式打开id表示的实体对象
            Try
                Dim acadEntity As Entity = CType(tm.GetObject(id, OpenMode.ForWrite), Entity)

                ' ed.WriteMessage(vbCrLf & acadEntity.IsWriteEnabled.ToString)

                acadEntity.TransformBy(mt)
                tm.Commit()
            Finally
                tm.Dispose()
            End Try

这样的语法才不会出错，这是什么原因呢？
查询objectid是有这个GetObject接口的。

zoomify

知道原因了：http://bbs.mjtd.com/forum.php?mod=viewthread&tid=108277