C#.NET AutoCAD2021API:访问给定BlockTable中的特定BlockTableRecords？

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

public class BlockTableRecordAccess
{
    [CommandMethod("AccessBlockTableRecord")]
    public void AccessBlockTableRecord()
    {
        // 获取当前文档和数据库对象
        Document doc = Application.DocumentManager.MdiActiveDocument;
        Database db = doc.Database;

        // 开启事务
        using (Transaction tr = db.TransactionManager.StartTransaction())
        {
            // 获取BlockTable对象
            BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;

            // 获取特定的BlockTableRecord
            string blockName = "MyBlock"; // 替换为要访问的BlockTableRecord的名称
            BlockTableRecord btr = tr.GetObject(bt[blockName], OpenMode.ForRead) as BlockTableRecord;

            // 对BlockTableRecord进行操作
            // 例如，访问属性
            string blockDescription = btr.Description;

            // 输出结果
            Editor ed = doc.Editor;
            ed.WriteMessage("BlockTableRecord Description: " + blockDescription);

            // 提交事务
            tr.Commit();
        }
    }
}