Add and read extended data

1, add the extended data

 Private  Sub adding extension data ( ByVal ENT of As the Entity, ByVal DictName of As  String , ByVal the TypedValue of As the TypedValue)

        If ent.ExtensionDictionary = Nothing Then
            ent.CreateExtensionDictionary()
        End If

        Using tr As Transaction = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Database.TransactionManager.StartTransaction
            Dim xDict As DatabaseServices.DBDictionary = tr.GetObject(ent.ExtensionDictionary, OpenMode.ForWrite)
            If Not xDict.Contains(DictName) Then
                xDict.UpgradeOpen()
                Dim xrec As New Xrecord
                Dim rb As New ResultBuffer
                rb.Add(TypedValue)
                xrec.Data = rb
                xDict.SetAt (DictName, xrec)
                tr.AddNewlyCreatedDBObject(xrec, True)
            End If
        End Using
    End Sub

2, the extension data read

Private Function 读取扩展数据(ByVal ent As Entity, ByVal DictName As String) As Object
        Dim doc As Autodesk.AutoCAD.ApplicationServices.Document = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument
        Using TR As Autodesk.AutoCAD.DatabaseServices.Transaction = doc.TransactionManager.StartTransaction
            If ent.ExtensionDictionary.IsNull Then
                Return Nothing
            Else
                Dim xDict As DBDictionary = CType(Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.TransactionManager.GetObject(ent.ExtensionDictionary, DatabaseServices.OpenMode.ForRead), DBDictionary)
                If xDict.Contains(DictName) Then
                    Dim xRecId As ObjectId = xDict.GetAt(DictName)
                    Dim xRec As Xrecord = CType(TR.GetObject(xRecId, DatabaseServices.OpenMode.ForRead), Xrecord)
                    Return xRec.Data.AsArray(0).Value
                Else
                    Return Nothing
                End If
            End If
        End Using
    End Function