Create Leader Lines (.NET)

You can create a leader line from any point or feature in a drawing and control its appearance. Leaders can be straight line segments or smooth spline curves. Leader color is controlled by the current dimension line color. Leader scale is controlled by the overall dimension scale set in the active dimension style. The type and size of the arrowhead, if one is present, is controlled by the arrowhead defined in the active style.

A small line known as a hook line usually connects the annotation to the leader. Hook lines appear with multiline text and feature control frames if the last leader line segment is at an angle greater than 15 degrees from horizontal. The hook line is the length of a single arrowhead. If the leader has no annotation, it has no hook line.

You create a leader by creating an instance of a Leader object. When you create an instance of a Leader object, its constructor does not accept any parameters. The AppendVertex method is used to define the position and length of the leader created.

Create a leader line

This example creates a leader line in model space. There is no annotation associated with the leader line.

VB.NET

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Geometry
 
<CommandMethod("CreateLeader")> _
Public Sub CreateLeader()
    '' Get the current 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 the leader
        Using acLdr As Leader = New Leader()
            acLdr.AppendVertex(New Point3d(0, 0, 0))
            acLdr.AppendVertex(New Point3d(4, 4, 0))
            acLdr.AppendVertex(New Point3d(4, 5, 0))
            acLdr.HasArrowHead = True

            '' Add the new object to Model space and the transaction
            acBlkTblRec.AppendEntity(acLdr)
            acTrans.AddNewlyCreatedDBObject(acLdr, True)
        End Using

        '' Commit the changes and dispose of the transaction
        acTrans.Commit()
    End Using
End Sub

C#

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
 
[CommandMethod("CreateLeader")]
public static void CreateLeader()
{
    // Get the current 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 the leader
        using (Leader acLdr = new Leader())
        {
            acLdr.AppendVertex(new Point3d(0, 0, 0));
            acLdr.AppendVertex(new Point3d(4, 4, 0));
            acLdr.AppendVertex(new Point3d(4, 5, 0));
            acLdr.HasArrowHead = true;

            // Add the new object to Model space and the transaction
            acBlkTblRec.AppendEntity(acLdr);
            acTrans.AddNewlyCreatedDBObject(acLdr, true);
        }

        // Commit the changes and dispose of the transaction
        acTrans.Commit();
    }
}

VBA/ActiveX Code Reference

Sub CreateLeader()
    Dim leaderObj As AcadLeader
    Dim points(0 To 8) As Double
    Dim leaderType As Integer
    Dim annotationObject As AcadObject
 
    points(0) = 0: points(1) = 0: points(2) = 0
    points(3) = 4: points(4) = 4: points(5) = 0
    points(6) = 4: points(7) = 5: points(8) = 0
    leaderType = acLineWithArrow
    Set annotationObject = Nothing
 
    ' Create the leader object in model space
    Set leaderObj = ThisDrawing.ModelSpace. _
                        AddLeader(points, annotationObject, leaderType)
 
    ZoomAll
End Sub