如何通过C# API为AutoCAD块定义中的属性设置多行文本属性？

现有一段C#代码用于创建带属性的AutoCAD块定义，第二个参数是存储属性名称及其可见性的字典。现在需要设置多行文本属性，让该属性在AutoCAD界面通过._battman命令查看块定义时生效，问如何通过C# API实现这一需求？

原代码如下：

internal void AddBlockDefinition(string blockName, OrderedDictionary attrNamesAndVisiblity, double height)
{
    Document doc = Autodesk.AutoCAD.ApplicationServices.Core.Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;

    using (Transaction tr = db.TransactionManager.StartTransaction())
    using (BlockTable blockTable = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead))
    using (BlockTableRecord modelSpace = (BlockTableRecord)tr.GetObject(blockTable[BlockTableRecord.ModelSpace], OpenMode.ForWrite))
    {
        BlockTableRecord newBlck = new BlockTableRecord();
        newBlck.Name = blockName;
        blockTable.UpgradeOpen();
        ObjectId btrId = blockTable.Add(newBlck);
        tr.AddNewlyCreatedDBObject(newBlck, true);

        string value = "";
        ObjectId style = new ObjectId();
        double y = 0;
        foreach (DictionaryEntry nameAndVis in attrNamesAndVisiblity)
        {
            Point3d position = new Point3d(0, y, 0);
            string tag = nameAndVis.Key.ToString();
            string prompt = tag;
            AttributeDefinition ad = new AttributeDefinition(position, value, tag, prompt, style);
            ad.Height = height;
            ad.Invisible = !((bool)nameAndVis.Value);
                    
            newBlck.AppendEntity(ad);
            tr.AddNewlyCreatedDBObject(ad, true);
            y = y - height * 1.3;
        }
        tr.Commit();
    }
}

要让块属性支持多行文本，关键是在创建AttributeDefinition时开启多行属性开关，并配置相关参数：

• 启用多行属性：将AttributeDefinition的MTextAttribute属性设为true，这是核心设置，告诉AutoCAD该属性是多行文本类型。
• 配置多行文本参数：
  • Width：设置多行文本框的宽度（可选，不设置的话会自动换行）；
  • MTextAttributeHeight：指定多行文本的行高（如果需要和单行文本区分的话，默认可以沿用Height的值）；
  • 若需要指定多行文字样式，可设置MTextAttributeStyle属性（需传入对应的文字样式ObjectId）。

修改后的代码示例（标注关键修改点）：

internal void AddBlockDefinition(string blockName, OrderedDictionary attrNamesAndVisiblity, double height)
{
    Document doc = Autodesk.AutoCAD.ApplicationServices.Core.Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;

    using (Transaction tr = db.TransactionManager.StartTransaction())
    using (BlockTable blockTable = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead))
    using (BlockTableRecord modelSpace = (BlockTableRecord)tr.GetObject(blockTable[BlockTableRecord.ModelSpace], OpenMode.ForWrite))
    {
        BlockTableRecord newBlck = new BlockTableRecord();
        newBlck.Name = blockName;
        blockTable.UpgradeOpen();
        ObjectId btrId = blockTable.Add(newBlck);
        tr.AddNewlyCreatedDBObject(newBlck, true);

        string value = "";
        ObjectId style = new ObjectId();
        // 可选：获取默认多行文字样式（如果需要自定义样式）
        // TextStyleTable textStyleTable = (TextStyleTable)tr.GetObject(db.TextStyleTableId, OpenMode.ForRead);
        // ObjectId mTextStyleId = textStyleTable["Standard"];

        double y = 0;
        foreach (DictionaryEntry nameAndVis in attrNamesAndVisiblity)
        {
            Point3d position = new Point3d(0, y, 0);
            string tag = nameAndVis.Key.ToString();
            string prompt = tag;
            AttributeDefinition ad = new AttributeDefinition(position, value, tag, prompt, style);
            ad.Height = height;
            ad.Invisible = !((bool)nameAndVis.Value);

            // -------------------------- 关键修改 --------------------------
            // 启用多行文本属性
            ad.MTextAttribute = true;
            // 设置多行文本框宽度（示例设为100，可根据需求调整）
            ad.Width = 100;
            // 可选：设置多行文本行高，默认和Height一致，也可单独指定
            // ad.MTextAttributeHeight = height;
            // 可选：指定多行文字样式
            // ad.MTextAttributeStyle = mTextStyleId;
            // -------------------------------------------------------------

            newBlck.AppendEntity(ad);
            tr.AddNewlyCreatedDBObject(ad, true);
            y = y - height * 1.3;
        }
        tr.Commit();
    }
}

完成上述修改后，用._battman命令查看块定义时，该属性会被识别为多行文本，插入块时也可以输入多行内容。

内容的提问来源于stack exchange，提问作者user2194358