升级和降级打开的对象 （.NET）

通过升级或降级对象，可以将对象的当前打开模式从读取更改为写入或从写入更改为读取。

这些方法可用于升级或降级以前打开的对象：

• Transaction.GetObject方法 – 如果使用该方法打开对象，请使用该方法以所需的新打开模式重新打开对象。Transaction.GetObject
• UpgradeOpenand方法 – 如果使用方法打开对象，或者使用方法将对象的打开模式从读取更改为写入，或者使用方法将对象的打开模式从写入更改为读取。您不需要将调用与每个配对，因为关闭对象或释放事务将充分清理对象的打开状态。DowngradeOpenOpenOpenCloseTransaction.GetObjectUpgradeOpenDowngradeOpenDowngradeOpenUpgradeOpen

建议使用最匹配对象使用方式的模式打开对象，因为打开对象进行读取和查询对象的属性比打开对象进行写入和查询对象的属性更有效。如果不确定是否需要修改对象，最好打开该对象进行读取，然后升级它以进行写入，因为这有助于减少程序的开销。

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
 
<CommandMethod("FreezeDoorLayer")> _
Public Sub FreezeDoorLayer()
    '' Get the current document and database
    Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
    Dim acCurDb As Database = acDoc.Database

    '' Start a transaction
    Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()

        '' Open the Layer table for read
        Dim acLyrTbl As LayerTable
        acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId, OpenMode.ForRead)

        '' Step through each layer and update those that start with 'Door'
        For Each acObjId As ObjectId In acLyrTbl
            '' Open the Layer table record for read
            Dim acLyrTblRec As LayerTableRecord
            acLyrTblRec = acTrans.GetObject(acObjId, OpenMode.ForRead)

            '' Check to see if the layer's name starts with 'Door' 
            If (acLyrTblRec.Name.StartsWith("Door", _
                                            StringComparison.OrdinalIgnoreCase) = True) Then
                '' Check to see if the layer is current, if so then do not freeze it
                If acLyrTblRec.ObjectId <> acCurDb.Clayer Then
                    '' Change from read to write mode
                    acTrans.GetObject(acObjId, OpenMode.ForWrite)

                    '' Freeze the layer
                    acLyrTblRec.IsFrozen = True
                End If
            End If
        Next

        '' Commit the changes and dispose of the transaction
        acTrans.Commit()
    End Using
End Sub

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
 
[CommandMethod("FreezeDoorLayer")]
public static void FreezeDoorLayer()
{
    // Get the current document and database
    Document acDoc = Application.DocumentManager.MdiActiveDocument;
    Database acCurDb = acDoc.Database;

    // Start a transaction
    using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
    {
        // Open the Layer table for read
        LayerTable acLyrTbl;
        acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId,
                                        OpenMode.ForRead) as LayerTable;

        // Step through each layer and update those that start with 'Door'
        foreach (ObjectId acObjId in acLyrTbl)
        {
            // Open the Layer table record for read
            LayerTableRecord acLyrTblRec;
            acLyrTblRec = acTrans.GetObject(acObjId,
                                            OpenMode.ForRead) as LayerTableRecord;

            // Check to see if the layer's name starts with 'Door' 
            if (acLyrTblRec.Name.StartsWith("Door",
                                            StringComparison.OrdinalIgnoreCase) == true)
            {
                // Check to see if the layer is current, if so then do not freeze it
                if (acLyrTblRec.ObjectId != acCurDb.Clayer)
                {
                    // Change from read to write mode
                    acTrans.GetObject(acObjId, OpenMode.ForWrite);

                    // Freeze the layer
                    acLyrTblRec.IsFrozen = true;
                }
            }
        }

        // Commit the changes and dispose of the transaction
        acTrans.Commit();
    }
}