Use Transactions to Access and Create Objects (.NET)

The Transaction Manager is accessed from the TransactionManager property of the current database. Once a reference to the Transaction Manager is made, you can use one of the following methods to start or obtain a transaction:

• StartTransaction – Starts a new transaction by creating a new instance of a Transaction object. Use this method when you need to write to an object multiple times and control how the changes can be rolled back through the use of different nesting levels.
• StartOpenCloseTransation – Creates an OpenCloseTransaction object, which behaves similar to a Transaction object, that wraps the Open and Close methods of an object making it easier to close all opened objects instead of having to explicitly close each opened object. Recommended for use in support or utility functions that might be called an unknown number of times, and used when working with most event handlers.

Once you have a Transaction or OpenCloseTransaction object, use the GetObject method to open an object stored in the database for read or write. The GetObject method returns a DBObject which can be cast to the actual object type it represents.

All open objects opened during a transaction are closed at the end of the transaction. To end a transaction, call the Dispose method of a transaction object. If you use the Using statement with the start of a transaction, you do not need to call the Dispose method.

Prior to disposing of a transaction, you should commit any changes made with the Commit method. If the changes are not committed before a transaction is disposed, any changes made are rolled back to the state they were in prior to the start of the transaction.

More than one transaction can be started. The number of active transactions can be retrieved with the NumberOfActiveTransactions property of the TransactionManager object while the top most or latest transaction can be retrieved with the TopTransaction property.

Transactions can be nested one inside of another in order to roll back some of the changes made during the execution of a routine.

Query objects

The following example demonstrates how to open and read objects within using a transaction. You use the GetObject method to first open the BlockTable and then the Model space record.

C# Example

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
 
[CommandMethod("StartTransactionManager")]
public static void StartTransactionManager()
{
    // 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 Block table for read
        BlockTable acBlkTbl;
        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                     OpenMode.ForRead) as BlockTable;
 
        // Open the Block table record Model space for read
        BlockTableRecord acBlkTblRec;
        acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                        OpenMode.ForRead) as BlockTableRecord;
 
        // Step through the Block table record
        foreach (ObjectId asObjId in acBlkTblRec)
        {
            acDoc.Editor.WriteMessage("\nDXF name: " + asObjId.ObjectClass.DxfName);
            acDoc.Editor.WriteMessage("\nObjectID: " + asObjId.ToString());
            acDoc.Editor.WriteMessage("\nHandle: " + asObjId.Handle.ToString());
            acDoc.Editor.WriteMessage("\n");
        }
 
        // Dispose of the transaction
    }
}

Add a new object to the database

The following example demonstrates how to add a circle object to the database with in a transaction. You use the GetObject method to first open the BlockTable for read and then the Model space record for write. After Model space is opened for write, you use the AppendEntity and AddNewlyCreatedDBObject function to append the new Circle object to Model space as well as the transaction.

C# Example

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

    // Start a transaction
    using (Transaction acTrans = acCurDb.TransactionManager.StartOpenCloseTransaction())
    {
        // Open the Block table for read
        BlockTable acBlkTbl;
        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                     OpenMode.ForRead) as BlockTable;

        // Open the Block table record Model space for write
        BlockTableRecord acBlkTblRec;
        acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                        OpenMode.ForWrite) as BlockTableRecord;

        // Create a circle with a radius of 3 at 5,5
        using (Circle acCirc = new Circle())
        {
            acCirc.Center = new Point3d(5, 5, 0);
            acCirc.Radius = 3;

            // Add the new object to Model space and the transaction
            acBlkTblRec.AppendEntity(acCirc);
            acTrans.AddNewlyCreatedDBObject(acCirc, true);
        }

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