net cad自动捕捉端点功能具体代码

下面是一个使用C#语言编写的.NET平台上的CAD应用程序的代码示例，实现了自动捕捉端点功能：

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Geometry;

namespace MyCADApp
{
    public class MyCommands
    {
        [CommandMethod("MyLine")]
        public void MyLine()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;
            Editor ed = doc.Editor;

            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
                BlockTableRecord btr = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForWrite);

                PromptPointOptions ppo1 = new PromptPointOptions("\nStart point: ");
                ppo1.UseBasePoint = true;
                ppo1.BasePoint = Point3d.Origin;
                ppo1.UseDashedLine = true;
                ppo1.AllowNone = true;
                ppo1.Keywords.Add("E");
                ppo1.Keywords.Add("X");
                ppo1.Keywords.Default = "E";

                PromptPointResult ppr1 = ed.GetPoint(ppo1);
                if (ppr1.Status != PromptStatus.OK) return;

                if (ppr1.Status == PromptStatus.Keyword)
                {
                    if (ppr1.StringResult == "X") return;
                    else if (ppr1.StringResult == "E")
                    {
                        ppo1.UseBasePoint = false;
                        ppo1.UseDashedLine = false;
                        ppo1.Message = "\nEndpoint: ";
                        ppo1.Keywords.Clear();
                    }
                }

                PromptPointOptions ppo2 = new PromptPointOptions("\nEnd point: ");
                ppo2.UseBasePoint = true;
                ppo2.BasePoint = ppr1.Value;
                ppo2.UseDashedLine = true;
                ppo2.AllowNone = true;
                ppo2.Keywords.Add("E");
                ppo2.Keywords.Add("X");
                ppo2.Keywords.Default = "E";

                PromptPointResult ppr2 = ed.GetPoint(ppo2);
                if (ppr2.Status != PromptStatus.OK) return;

                if (ppr2.Status == PromptStatus.Keyword)
                {
                    if (ppr2.StringResult == "X") return;
                    else if (ppr2.StringResult == "E")
                    {
                        ppo2.UseBasePoint = false;
                        ppo2.UseDashedLine = false;
                        ppo2.Message = "\nEndpoint: ";
                        ppo2.Keywords.Clear();
                    }
                }

                Line line = new Line(ppr1.Value, ppr2.Value);

                btr.AppendEntity(line);
                tr.AddNewlyCreatedDBObject(line, true);

                tr.Commit();
            }
        }
    }
}

在这个代码示例中，使用了AutoCAD的API中的PromptPointOptions类的UseBasePoint属性和UseDashedLine属性来实现自动捕捉端点功能。在获取起点坐标时，设置UseBasePoint属性为true，并将BasePoint属性设置为原点，同时设置UseDashedLine属性为true，这样在鼠标移动过程中，会自动捕捉到距离原点最近的端点。在获取终点坐标时，设置UseBasePoint属性为true，并将BasePoint属性设置为起点坐标，同时设置UseDashedLine属性为true，这样在鼠标移动过程中，会自动捕捉到距离起点坐标最近的端点。通过使用PromptPointOptions类的Keywords属性，可以添加关键字，实现在命令过程中的交互。