我不是要获取图形中标注的样式，是想要当前默认的标注样式

非常抱歉，我理解有误。以下是获取当前默认标注样式名称的 C# 代码：

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

namespace GetCurrentDimensionStyleName
{
    public class Commands
    {
        [CommandMethod("GetCurrentDimensionStyleName")]
        public static void GetCurrentDimensionStyleName()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Editor ed = doc.Editor;
            Database db = doc.Database;

            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                DimStyleTable dst = tr.GetObject(db.DimStyleTableId, OpenMode.ForRead) as DimStyleTable;
                DimStyleTableRecord currentDst = tr.GetObject(dst.CurrentStyle, OpenMode.ForRead) as DimStyleTableRecord;

                ed.WriteMessage("\nCurrent default dimension style name: " + currentDst.Name);

                tr.Commit();
            }
        }
    }
}

该代码使用了 AutoCAD API，首先获取当前文档、编辑器和数据库，然后在事务中获取当前的标注样式表和默认标注样式记录，并输出当前默认标注样式的名称。