如下图所示，红线为分割后的线（已挪动）：

 部分代码如下：

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Runtime;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using AcTools;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Colors;
using System.Runtime.CompilerServices;
using Wform = System.Windows.Forms;
using System.IO;
using System.Windows.Forms;
//using Excel = NetOffice.ExcelApi;

namespace AcTools
{

    public class Class1
    {
        #region 
        //Polyline pl = new Polyline(3);
        //pl.AddVertexAt(0, new Point2d(10, 2), 0, 0, 0); // 起点 
        //pl.AddVertexAt(1, new Point2d(30, 5), 0, 0, 0); // 起点 
        //pl.AddVertexAt(2, new Point2d(50, 25), 0, 0, 0); // 起点 
        //Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
        //db.AddEntityToModeSpace(line);
        #endregion
        [CommandMethod("xx")]
        public void XX()
        {   var db = Z.db;
            Point3dCollection pcoll = new Point3dCollection();
            List<Entity> ents =db.SelectEntities<Entity>();
            if (ents.Count<1)
            {
                Z.ed.WriteMessage("重新选择"); 
            }
                for (global::System.Int32 i = 0; i < ents.Count; i++)
                {
                    for (global::System.Int32 j = i+1; j < ents.Count; j++)
                    {
                        ents[i].IntersectWith(ents[j], Intersect.OnBothOperands, pcoll, IntPtr.Zero, IntPtr.Zero); 
                    }
                }
                if (pcoll.Count ==0)
                {
                    return; 
                }
                //foreach (Point3d item in pcoll)
                //{
                //    db.AddCircleModeSpace(item, 2);
                //}
            foreach (Curve item1 in ents)
            { 
                    try
                    {
                        DBObjectCollection dBoc= item1.GetSplitCurves(pcoll);
                        foreach (Entity entsp in dBoc)
                        {
                            db.AddEntityToModeSpace(entsp);
                            entsp.ChangeEntityColor(1);
                        }
                  
                    }
                    
                    catch (System.Exception)
                    {

                        Z.ed.WriteMessage("无\n");
                    }
                //db.Erase(item1);    
               
                
            }
           
        }