Iterate through a Collection Object

To select a specific member of a Collection object, use the Item or GetAt method. The Item and GetAt methods require a key in the form of a string in which represents the name of the item. With most collections, the Item method is implied, meaning you do not actually need to use method.

With some Collection objects, you can also use an index number to specify the location of the item within the collection you want to retrieve. The method you can use varies based on the language you are using as well as if you are working with a symbol table or dictionary.

The following statements show how to access the “MyLayer” table record in Layer symbol table.

VB.NET

acObjId = acLyrTbl.Item("MyLayer")

acObjId = acLyrTbl("MyLayer")

acObjId = acLyrTbl["MyLayer"];

VBA/ActiveX Code Reference

Iterate through the LayerTable object

The following example iterates through the LayerTable object and displays the names of all its layer table records:

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

<CommandMethod("IterateLayers")> _

Public Sub IterateLayers()

  '' 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()

      '' This example returns the layer table for the current database

      Dim acLyrTbl As LayerTable

      acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId, _

                                   OpenMode.ForRead)

      '' Step through the Layer table and print each layer name

      For Each acObjId As ObjectId In acLyrTbl

          Dim acLyrTblRec As LayerTableRecord

          acLyrTblRec = acTrans.GetObject(acObjId, OpenMode.ForRead)

          acDoc.Editor.WriteMessage(vbLf & acLyrTblRec.Name)

      Next

      '' Dispose of the transaction

  End Using

End Sub

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

[CommandMethod("IterateLayers")]

public static void IterateLayers()

  // 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())

      // This example returns the layer table for the current database

      LayerTable acLyrTbl;

      acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId,

                                   OpenMode.ForRead) as LayerTable;

      // Step through the Layer table and print each layer name

      foreach (ObjectId acObjId in acLyrTbl)

          LayerTableRecord acLyrTblRec;

          acLyrTblRec = acTrans.GetObject(acObjId,

                                          OpenMode.ForRead) as LayerTableRecord;

          acDoc.Editor.WriteMessage("\n" + acLyrTblRec.Name);

      // Dispose of the transaction

VBA/ActiveX Code Reference

Find the layer table record named MyLayer in the LayerTable object

The following example checks the LayerTable object to determine if the layer named MyLayer exists or not, and displays the appropriate message:

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

<CommandMethod("FindMyLayer")> _

Public Sub FindMyLayer()

  '' 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 Not acLyrTbl.Has("MyLayer") Then

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

      Else

          acDoc.Editor.WriteMessage(vbLf & "'MyLayer' exists")

      End If

      '' Dispose of the transaction

  End Using

End Sub

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

[CommandMethod("FindMyLayer")]

public static void FindMyLayer()

  // 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)

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

      else

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

      // Dispose of the transaction

VBA/ActiveX Code Reference