AutoCAD二次开发（.Net）之多重引线（MLeader）创建

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

        [CommandMethod("CREATEMLEADER")]
        public void CreateMLeader()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Editor ed = doc.Editor;
            Database db = doc.Database;
            const string arrowName = "_DOT";
            ObjectId arrId = GetArrowObjectId(arrowName);

            // Get the start point of the leader
            PromptPointResult result =ed.GetPoint("/n 选择标注起始位置: " );
            if (result.Status != PromptStatus.OK)
                return;
            Point3d startPt = result.Value;

            // Get the end point of the leader
            PromptPointOptions opts =new PromptPointOptions("/n选择标注终止位置: ");
            opts.BasePoint = startPt;
            opts.UseBasePoint = true;
            result = ed.GetPoint(opts);
            if (result.Status != PromptStatus.OK)
                return;
            Point3d endPt = result.Value;

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

                    // Create the MLeader
                    MLeader mld = new MLeader();
                    int ldNum = mld.AddLeader();
                    int lnNum = mld.AddLeaderLine(ldNum);
                    mld.AddFirstVertex(lnNum, startPt);
                    mld.AddLastVertex(lnNum, endPt);
                    mld.ArrowSymbolId = arrId;
                    mld.LeaderLineType = LeaderType.SplineLeader;

                    // Create the MText
                    MText mt = new MText();
                    mt.Contents = "ABC";
                    mt.Location = endPt;
                    mld.ContentType = ContentType.MTextContent;
                    mld.MText = mt;

                    // Add the MLeader
                    btr.AppendEntity(mld);
                    tr.AddNewlyCreatedDBObject(mld, true);
                    tr.Commit();
                }
                catch
                {
                    // Would also happen automatically
                    // if we didn't commit
                    tr.Abort();
                }
            }
        }
        static ObjectId GetArrowObjectId(string newArrName)
        {
            ObjectId arrObjId = ObjectId.Null;

            Document doc = Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;

            // Get the current value of DIMBLK
            string oldArrName = Application.GetSystemVariable("DIMBLK") as string;

            // Set DIMBLK to the new style
            // (this action may create a new block)
            Application.SetSystemVariable("DIMBLK", newArrName);

            // Reset the previous value of DIMBLK
            if (oldArrName.Length != 0)
                Application.SetSystemVariable("DIMBLK", oldArrName);

            // Now get the objectId of the block
            Transaction tr = db.TransactionManager.StartTransaction();
            using (tr)
            {
                BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
                arrObjId = bt[newArrName];
                tr.Commit();
            }
            return arrObjId;
        }