ArcGIS Pro 2.7 API Reference Guide
StartPoint Property (LineBuilder)
Example 

ArcGIS.Core.Geometry Namespace > LineBuilder Class : StartPoint Property
Gets or sets the start point of the line segment.
Syntax
public MapPoint StartPoint {get; set;}
Public Property StartPoint As MapPoint

Property Value

A MapPoint representing the start point.
Exceptions
ExceptionDescription
This method or property must be called within the lambda passed to QueuedTask.Run.
Setting the start point with a null object.
Remarks

Line Segment

Example
// Builder constructors need to run on the MCT.
ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
{
  // use the builder constructor
  using (LineBuilder lb = new LineBuilder(lineSegment))
  {
    // find the existing coordinates
    lb.QueryCoords(out startPt, out endPt);

    // or use 
    //startPt = lb.StartPoint;
    //endPt = lb.EndPoint;

    // update the coordinates
    lb.SetCoords(GeometryEngine.Instance.Move(startPt, 10, 10) as MapPoint, GeometryEngine.Instance.Move(endPt, -10, -10) as MapPoint);

    // or use 
    //lb.StartPoint = GeometryEngine.Instance.Move(startPt, 10, 10) as MapPoint;
    //lb.EndPoint = GeometryEngine.Instance.Move(endPt, -10, -10) as MapPoint;

    LineSegment anotherLineSegment = lb.ToSegment();
  }
});
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

LineBuilder Class
LineBuilder Members