Polyline2d和Polyline3d的点更改,它和其他的图元处理起来不一样.
因为这些是复杂实体,需要通过枚举值来处理.

提取点集

先看一个通用的提取点集的做法,
GetStretchPoints可以作用在:轻多段线/二维多段线/三维多段线
你只需要将Polyline2d改成其他即可.
之所以改成List<Point3d>是因为用上Linq,微软大法好啊!

/// <summary>
/// 二维多段线点集
/// </summary> 
public static List<Point3d> GetPoint3ds(this Polyline2d pl)
{
    var pts3d = new Point3dCollection();
    pl.GetStretchPoints(pts3d);

    var lst = new List<Point3d>();
    foreach (Point3d item in pts3d)
    {
        lst.Add(item);
    }
    return lst;
}

将二维多段线的点集逆序

IsClockwise 判断是否顺时针,可参考叉乘判断

//打开图元
var ent = tr.GetObject(item, OpenMode.ForWrite) as Entity;                              
if (ent is Polyline2d pl2d)
{
    var pts3d = pl2d.GetPoint3ds();
    if (!IsClockwise(pts3d))//判断是否顺时针
    {
        continue;
    }

    int j = 0;
    var pl2dEnu = pl2d.GetEnumerator();
    while (pl2dEnu.MoveNext())
    { 
        if (j > 0)
        {
            var id = (ObjectId)pl2dEnu.Current;
            var vtx = tr.GetObject(id, OpenMode.ForWrite) as Vertex2d;
            vtx.Position = pts3d[pts3d.Count - j];
        }
        j++;
    }
}

(完)

cad.net 替换Polyline2d的点