Extend and Trim Objects
 
 
 

You can change the angle of arcs and you can change the length of lines, open polylines, elliptical arcs, and open splines. The results are similar to both extending and trimming objects.

You can extend or trim an object by editing its properties. For example, to lengthen a line, simply change the coordinates of the StartPoint or EndPoint properties. To change the angle of an arc, change the StartAngle or EndAngle property of the arc. Once you have altered an object's property or properties, you might need to regenerate the display to see the changes in the drawing window.

For more information about extending and trimming objects, see “Resize or Reshape Objects” in the AutoCAD User's Guide.

Lengthen a line

This example creates a line and then changes the endpoint of that line, resulting in a longer line.

VB.NET

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Geometry
 
<CommandMethod("ExtendObject")> _
Public Sub ExtendObject()
  '' Get the current document and database
  Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
  Dim acCurDb As Database = acDoc.Database
 
  '' Start a transaction
  Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
 
      '' Open the Block table for read
      Dim acBlkTbl As BlockTable
      acBlkTbl = acTrans.GetObject(acCurDb.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 line that starts at (4,4,0) and ends at (7,7,0)
      Dim acLine As Line = New Line(New Point3d(4, 4, 0), _
                                    New Point3d(7, 7, 0))
 
      acLine.SetDatabaseDefaults()
 
      '' Add the new object to the block table record and the transaction
      acBlkTblRec.AppendEntity(acLine)
      acTrans.AddNewlyCreatedDBObject(acLine, True)
 
      '' Update the display and diaplay a message box
      acDoc.Editor.Regen()
      Application.ShowAlertDialog("Before extend")
 
      '' Double the length of the line
      acLine.EndPoint = acLine.EndPoint + acLine.Delta
 
      '' Save the new object to the database
      acTrans.Commit()
  End Using
End Sub

C#

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
 
[CommandMethod("ExtendObject")]
public static void ExtendObject()
{
  // 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 write
      BlockTableRecord acBlkTblRec;
      acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                      OpenMode.ForWrite) as BlockTableRecord;
 
      // Create a line that starts at (4,4,0) and ends at (7,7,0)
      Line acLine = new Line(new Point3d(4, 4, 0),
                             new Point3d(7, 7, 0));
 
      acLine.SetDatabaseDefaults();
 
      // Add the new object to the block table record and the transaction
      acBlkTblRec.AppendEntity(acLine);
      acTrans.AddNewlyCreatedDBObject(acLine, true);
 
      // Update the display and diaplay a message box
      acDoc.Editor.Regen();
      Application.ShowAlertDialog("Before extend");
 
      // Double the length of the line
      acLine.EndPoint = acLine.EndPoint + acLine.Delta;
 
      // Save the new object to the database
      acTrans.Commit();
  }
}
VBA/ActiveX Code Reference