Reference Objects in the Object Hierarchy

When you work with objects in the .NET API, you can reference some objects directly or through a user-defined variable based on the object you are working with. To reference an objects directly, include the object in the calling hierarchy. For example, the following statement attaches a drawing file to the database of the current drawing. Notice that the hierarchy starts with the Application and then goes to the Database object. From the Database object, the AttachXref method is called:

VB.NET

Dim strFName As String, strBlkName As String

Dim objId As Autodesk.AutoCAD.DatabaseServices.ObjectId

strFName = "c:\clients\Proj 123\grid.dwg"

strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName)

objId = Application.DocumentManager.MdiActiveDocument.Database.AttachXref(strFName, strBlkName)

string strFName, strBlkName;

Autodesk.AutoCAD.DatabaseServices.ObjectId objId;

strFName = "c:/clients/Proj 123/grid.dwg";

strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName);

objId = Application.DocumentManager.MdiActiveDocument.Database.AttachXref(strFName, strBlkName);

To reference the objects through a user-defined variable, define the variable as the desired type, then set the variable to the appropriate object. For example, the following code defines a variable (acCurDb) of type Autodesk.AutoCAD.DatabaseServices.Database and sets the variable equal to the current database:

VB.NET

Dim acCurDb As Autodesk.AutoCAD.DatabaseServices.Database

acCurDb = Application.DocumentManager.MdiActiveDocument.Database

Autodesk.AutoCAD.DatabaseServices.Database acCurDb;

acCurDb = Application.DocumentManager.MdiActiveDocument.Database;

The following statement then attaches a drawing file to the database using the acCurDb user-defined variable:

VB.NET

Dim strFName As String, strBlkName As String

Dim objId As Autodesk.AutoCAD.DatabaseServices.ObjectId

strFName = "c:\clients\Proj 123\grid.dwg"

strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName)

objId = acCurDb.AttachXref(strFName, strBlkName)

string strFName, strBlkName;

Autodesk.AutoCAD.DatabaseServices.ObjectId objId;

strFName = "c:/clients/Proj 123/grid.dwg";

strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName);

objId = acCurDb.AttachXref(strFName, strBlkName);

Retrieve entities from Model space

The following example returns the first entity object in Model space. Similar code can do the same for Paper space entities. Note that all graphical objects are defined as an Entity object:

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

<CommandMethod("ListEntities")> _

Public Sub ListEntities()

  '' 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()

      '' Open the Block table record for read

      Dim acBlkTbl As BlockTable

      acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, _

                                   OpenMode.ForRead)

      '' Open the Block table record Model space for read

      Dim acBlkTblRec As BlockTableRecord

      acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), _

                                      OpenMode.ForRead)

      Dim nCnt As Integer = 0

      acDoc.Editor.WriteMessage(vbLf & "Model space objects: ")

      '' Step through each object in Model space and

      '' display the type of object found

      For Each acObjId As ObjectId In acBlkTblRec

          acDoc.Editor.WriteMessage(vbLf & acObjId.ObjectClass().DxfName)

          nCnt = nCnt + 1

      Next

      '' If no objects are found then display the following message

      If nCnt = 0 Then

          acDoc.Editor.WriteMessage(vbLf & "  No objects found")

      End If

      '' Dispose of the transaction

  End Using

End Sub

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

[CommandMethod("ListEntities")]

public static void ListEntities()

  // 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())

      // Open the Block table record 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;

      int nCnt = 0;

      acDoc.Editor.WriteMessage("\nModel space objects: ");

      // Step through each object in Model space and

      // display the type of object found

      foreach (ObjectId acObjId in acBlkTblRec)

          acDoc.Editor.WriteMessage("\n" + acObjId.ObjectClass.DxfName);

          nCnt = nCnt + 1;

      // If no objects are found then display a message

      if (nCnt == 0)

          acDoc.Editor.WriteMessage("\n No objects found");

      // Dispose of the transaction

VBA/ActiveX Code Reference