You can easily redraw this polyline, if this one
is have the straight segments only, here is a quick code for this case:
' for using to updating a straight polyline segments only
<CommandMethod("repst", CommandFlags.Redraw)> _
Public Shared Sub TestChangePolyStart()
Dim doc As Document = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument
Dim ed As Editor = doc.Editor
Dim db As Database = doc.Database
Dim ucs As CoordinateSystem3d = ed.CurrentUserCoordinateSystem.CoordinateSystem3d
Dim osm As Object = Nothing
Dim mat As Matrix3d = Matrix3d.AlignCoordinateSystem(Point3d.Origin, Vector3d.XAxis, Vector3d.YAxis, Vector3d.ZAxis, ucs.Origin, ucs.Xaxis, _
ucs.Yaxis, ucs.Zaxis)
Try
Using doclock As DocumentLock = doc.LockDocument()
osm = Autodesk.AutoCAD.ApplicationServices.Application.GetSystemVariable("osmode")
Autodesk.AutoCAD.ApplicationServices.Application.SetSystemVariable("osmode", 1)
Dim peo1 As New PromptEntityOptions(vbLf & "Select a polyline : ")
peo1.SetRejectMessage(vbLf & "You have to select polyline only!")
peo1.AddAllowedClass(GetType(Polyline), False)
Dim res1 As PromptEntityResult = ed.GetEntity(peo1)
If res1.Status <> PromptStatus.OK Then
Return
End If
Dim id As ObjectId = res1.ObjectId
Dim p1 As Point3d = res1.PickedPoint.TransformBy(mat)
Dim prOpt As New PromptPointOptions(vbLf & "Pick a new start vertex point: ")
Dim es As PromptPointResult = ed.GetPoint(prOpt)
If es.Status <> PromptStatus.OK Then
If es.Status = PromptStatus.Cancel Then
ed.WriteMessage(vbLf & "Interrupted by user")
Return
Else
ed.WriteMessage(vbLf & "Error on specifying a point")
Return
End If
End If
Dim new3dPt As Point3d = es.Value.TransformBy(mat)
Using tr As Transaction = db.TransactionManager.StartTransaction()
Dim poly As Polyline = DirectCast(tr.GetObject(id, OpenMode.ForRead), Polyline)
Dim wid As Double = poly.ConstantWidth
Dim new2dPt As New Point2d(new3dPt.X, new3dPt.Y)
Dim c As Integer = 0
Dim points As New List(Of Point2d)()
Dim sb As New StringBuilder()
For c = 0 To poly.NumberOfVertices - 1
points.Add(poly.GetPoint2dAt(c))
Next
Dim pos As Integer = points.IndexOf(new2dPt)
'Reverse List from given position using LINQ implementation
Dim tail As IEnumerable(Of Point2d) = points.Take(pos)
Dim head As IEnumerable(Of Point2d) = points.Except(tail)
Dim newpoints As IEnumerable(Of Point2d) = head.Concat(tail)
Dim pts As List(Of Point2d) = newpoints.ToList()
'________________________________________
Dim btr As BlockTableRecord = DirectCast(tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite), BlockTableRecord)
poly.UpgradeOpen()
Dim newpoly As New Polyline(poly.NumberOfVertices)
newpoly.Closed = poly.Closed
For c = 0 To pts.Count - 1
newpoly.AddVertexAt(c, CType(pts(c), Point2d), 0, wid, wid)
Next
newpoly.Closed = poly.Closed
btr.AppendEntity(newpoly)
tr.AddNewlyCreatedDBObject(newpoly, True)
newpoly.SetPropertiesFrom(poly)
poly.Erase()
tr.Commit()
ed.Regen()
End Using
End Using
Catch ex As System.Exception
ed.WriteMessage(vbLf & "{0}", ex.StackTrace)
Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor.WriteMessage(vbLf & "{0}" & vbLf & "{1}" & vbLf, ex.Message, ex.StackTrace)
Finally
Autodesk.AutoCAD.ApplicationServices.Application.SetSystemVariable("osmode", osm)
End Try
End Sub
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