Erase a Member of a Collection Object

Members from a collection object can be erased using the Erase method found on the member object. For example, the following code erases the layer MyLayer from the LayerTable object.

Before you erase a layer from a drawing, you should make sure it can be safely removed. To determine if a layer or another named object such as a block or text style can be erased, you should use the Purge method. For information on the Purge method, see Purge Unreferenced Named Objects.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

<CommandMethod("RemoveMyLayer")> _

Public Sub RemoveMyLayer()

  '' Get the current document and database, and start a transaction

  Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument

  Dim acCurDb As Database = acDoc.Database

  Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()

      '' Returns the layer table for the current database

      Dim acLyrTbl As LayerTable

      acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId, _

                                   OpenMode.ForRead)

      '' Check to see if MyLayer exists in the Layer table

      If acLyrTbl.Has("MyLayer") = True Then

          Dim acLyrTblRec As LayerTableRecord

          acLyrTblRec = acTrans.GetObject(acLyrTbl("MyLayer"), _

                                          OpenMode.ForWrite)

Try

              acLyrTblRec.Erase()

              acDoc.Editor.WriteMessage(vbLf & "'MyLayer' was erased")

              '' Commit the changes

              acTrans.Commit()

          Catch

              acDoc.Editor.WriteMessage(vbLf & "'MyLayer' could not be erased")

          End Try

      Else

          acDoc.Editor.WriteMessage(vbLf & "'MyLayer' does not exist")

      End If

      '' Dispose of the transaction

  End Using

End Sub

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

[CommandMethod("RemoveMyLayer")]

public static void RemoveMyLayer()

  // Get the current document and database, and start a transaction

  Document acDoc = Application.DocumentManager.MdiActiveDocument;

  Database acCurDb = acDoc.Database;

  using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())

      // Returns the layer table for the current database

      LayerTable acLyrTbl;

      acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId,

                                   OpenMode.ForRead) as LayerTable;

      // Check to see if MyLayer exists in the Layer table

      if (acLyrTbl.Has("MyLayer") == true)

          LayerTableRecord acLyrTblRec;

          acLyrTblRec = acTrans.GetObject(acLyrTbl["MyLayer"],

                                          OpenMode.ForWrite) as LayerTableRecord;

try

              acLyrTblRec.Erase();

              acDoc.Editor.WriteMessage("\n'MyLayer' was erased");

              // Commit the changes

              acTrans.Commit();

          catch

              acDoc.Editor.WriteMessage("\n'MyLayer' could not be erased");

      else

          acDoc.Editor.WriteMessage("\n'MyLayer' does not exist");

      // Dispose of the transaction

VBA/ActiveX Code Reference

Once an object has been erased, you should not attempt to access the object again later in the program; otherwise an error will occur. The above sample tests to see if the object exists before it is accessed again. When a request to erase an object is made, you should check to see if the object exists with the Has method or use a Try statement to catch any exceptions that occur. For more information on handling exceptions, see Handle Errors.