Extend and Trim Objects (.NET)

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.

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)
        Using acLine As Line = New Line(New Point3d(4, 4, 0), _
                                        New Point3d(7, 7, 0))

            '' 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
        End Using

        '' 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)
        using (Line acLine = new Line(new Point3d(4, 4, 0),
                                new Point3d(7, 7, 0)))
        {

            // 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

Sub ExtendObject()
    ' Define and create the line
    Dim lineObj As AcadLine
    Dim startPoint(0 To 2) As Double
    Dim endPoint(0 To 2)  As Double
    startPoint(0) = 4
    startPoint(1) = 4
    startPoint(2) = 0
    endPoint(0) = 7
    endPoint(1) = 7
    endPoint(2) = 0
    Set lineObj = ThisDrawing.ModelSpace. _
                                AddLine(startPoint, endPoint)
    lineObj.Update
 
    ' Double the length of the line
    endPoint(0) = lineObj.endPoint(0) + lineObj.Delta(0)
    endPoint(1) = lineObj.endPoint(1) + lineObj.Delta(1)
    endPoint(2) = lineObj.endPoint(2) + lineObj.Delta(2)
    lineObj.endPoint = endPoint
    lineObj.Update
End Sub