Upgrade and Downgrade Open Objects (.NET)

An object's current open mode can be changed from read to write or write to read by upgrading or downgrading the object.

These methods can be used to upgrade or downgrade a previously opened object:

• Transaction.GetObject method – If the object was opened with the Transaction.GetObject method, use the method to reopen the object with the desired new open mode.
• UpgradeOpen and DowngradeOpen methods – If the object was opened with the Open method, or the OpenCloseTransaction.GetObject, use the UpgradeOpen method to change the object’s open mode from read to write or DowngradeOpen method to change the object’s open mode from write to read. You do not need to pair a call to DowngradeOpen with each UpgradeOpen, since closing of an object or disposing of a transaction will sufficiently cleanup the open state of an object.

It is recommended to open an object with the mode that best matches how the object will be used, as it is more efficient to open an object for read and query the object’s properties than it is to open the object for write and query the object’s properties. If you are uncertain whether an object might need to be modified, it is best to open the object for read and then upgrade it for write as this helps to reduce the overhead of your program.

VB.NET

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

C#

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();
    }
}