Requests to modify objects or access AutoCAD can occur in any context, and coming from any number of applications. To prevent conflicts with other requests, you are responsible for locking a document before you modify it. Failure to lock the document in certain contexts will cause a lock violation during the modification of the database. You want to lock the document when your application:
For example, when adding an entity to Model or Paper space in a document other than the current document, the document needs to be locked. You use the LockDocument method of the Database object you want to lock. When the LockDocument method is called, a DocumentLock object is returned.
Once you are done modifying the locked database, you need to unlock the database. To unlock the database, you call the Dispose method of the DocumentLock object. You can also use the Using statement with the DocumentLock object, once the Using statement ends the database is unlocked.
Lock a database before modifying an object
This example creates a new document and then draws a circle in it. After the document is created, the database for the new document is locked and then a circle is added to it. After the circle is added, the database is unlocked and the associated document window is set current.
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.Geometry
<CommandMethod("LockDoc", CommandFlags.Session)> _
Public Sub LockDoc()
'' Create a new drawing
Dim acDocMgr As DocumentCollection = Application.DocumentManager
Dim acNewDoc As Document = acDocMgr.Add("acad.dwt")
Dim acDbNewDoc As Database = acNewDoc.Database
'' Lock the new document
Using acLckDoc As DocumentLock = acNewDoc.LockDocument()
'' Start a transaction in the new database
Using acTrans As Transaction = acDbNewDoc.TransactionManager.StartTransaction()
'' Open the Block table for read
Dim acBlkTbl As BlockTable
acBlkTbl = acTrans.GetObject(acDbNewDoc.BlockTableId, _
OpenMode.ForRead)
'' Open the Block table record Model space for write
Dim acBlkTblRec As BlockTableRecord
acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), _
OpenMode.ForWrite)
'' Create a circle with a radius of 3 at 5,5
Dim acCirc As Circle = 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)
'' Save the new object to the database
acTrans.Commit()
End Using
'' Unlock the document
End Using
'' Set the new document current
acDocMgr.MdiActiveDocument = acNewDoc
End Sub
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.Geometry;
[CommandMethod("LockDoc", CommandFlags.Session)]
public static void LockDoc()
{
// Create a new drawing
DocumentCollection acDocMgr = Application.DocumentManager;
Document acNewDoc = acDocMgr.Add("acad.dwt");
Database acDbNewDoc = acNewDoc.Database;
// Lock the new document
using (DocumentLock acLckDoc = acNewDoc.LockDocument())
{
// Start a transaction in the new database
using (Transaction acTrans = acDbNewDoc.TransactionManager.StartTransaction())
{
// Open the Block table for read
BlockTable acBlkTbl;
acBlkTbl = acTrans.GetObject(acDbNewDoc.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
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);
// Save the new object to the database
acTrans.Commit();
}
// Unlock the document
}
// Set the new document current
acDocMgr.MdiActiveDocument = acNewDoc;
}