CAD .net二次开发直线转化多段线（Polyline）

Point3dCollection col_point = new Point3dCollection();
Line ent_line = item as Line;
Point3d startPoint = ent_line.StartPoint;
Point3d endPoint = ent_line.EndPoint;
col_point.Add(startPoint);
col_point.Add(endPoint);

Polyline poly = new Polyline();

poly.Color = reg.Color;
poly.Closed = true;
poly.LineWeight = reg.LineWeight;
poly.LinetypeId = reg.LinetypeId;
PolylineTools.CreatePolyline(poly, col_point);

btr.AppendEntity(poly);
trans.AddNewlyCreatedDBObject(poly, true);

/// <summary>
/// 通过三维点集合创建多段线
/// </summary>
/// <param name="pline">多段线对象</param>
/// <param name="point3dCol">多段线的顶点</param>
public static void CreatePolyline(Polyline pline, Point3dCollection point3dCol)
{
   for (int i = 0; i < point3dCol.Count; i++)
       {
          //添加多段线的顶点
          pline.AddVertexAt(i, new Point2d(point3dCol[i].X, point3dCol[i].Y), 0, 0, 0);
       }
}