如何格式化列表文件夹的JSON输出，该文件夹也具有文件夹列表的属性

Question

我的数据库中有一个文件夹列表，其中包含文件夹列表等，如下所示：

在我的服务方法中检索JSON，我返回一个文件夹列表。

我想收到以下结构：

目前，这是生成文件夹列表的方法：

 public List<FolderStructureDTO> GetFolderStructureDTOs()
    {
        var folders = GetFolders();

        foreach (var folder in folders)
        {
            var bookmarks = db.Bookmarks.OfType<Folder>().Where(x => x.ParentId == folder.Id).ToList();

            foreach (var item in bookmarks)
            {
                folder.FolderBookmarks.Add(item);
            }
        }

        List<FolderStructureDTO> folderDTOs = null;

        foreach (var folder in folders)
        {
            folderDTOs = folders.Select(x => new FolderStructureDTO() { Folder = folder.Name, Subfolders = folder.FolderBookmarks }).ToList();

        }

        return folderDTOs;
    }

public class FolderStructureDTO
{
    public string Folder { get; set; }
    public List<Bookmark> Subfolders { get; set; }
}

这是我收到的输出JSON：

{"FolderBookmarks":[{"FolderBookmarks":[],"Id":123,"Name":"NonFiction","ParentId":122},{"FolderBookmarks":[{"FolderBookmarks":[],"Id":125,"Name":"Romance","ParentId":124},{"FolderBookmarks":[],"Id":126,"Name":"Horror","ParentId":124}],"Id":124,"Name":"Fiction","ParentId":122}],"Id":122,"Name":"Books","ParentId":101}

为了使它看起来更具可读性，这里是相同的JSON，但使用https://codebeautify.org/jsonviewer进行了美化：

{
"FolderBookmarks": [
    {
        "FolderBookmarks": [],
        "Id": 123,
        "Name": "NonFiction",
        "ParentId": 122
    },
    {
        "FolderBookmarks": [
            {
                "FolderBookmarks": [],
                "Id": 125,
                "Name": "Romance",
                "ParentId": 124
            },
            {
                "FolderBookmarks": [],
                "Id": 126,
                "Name": "Horror",
                "ParentId": 124
            }
        ],
        "Id": 124,
        "Name": "Fiction",
        "ParentId": 122
    }
],
"Id": 122,
"Name": "Books",
"ParentId": 101
}

任何人都可以帮我生成所需的JSON格式吗？我环顾四周，无法找到解决方案。