Read folders recursively in .Net Core

file-reader.cs

namespace App
{
  public class FileReader
  {
    private List<FolderModel> GetFoldersForDocs()
    {
      DirectoryInfo di = new DirectoryInfo(documentationPath);
      FileInfo[] files = RecursiveFetch(4, di.FullName);
      var trimLength = di.FullName.Count();
      var folders =  files.Select(x => BuildFileModel(x, trimLength))
                          .Distinct()
                          .GroupBy(file => file.pathParts[0],
                            file => file,
                            (key, fileGroup) => BuildFolder(key, fileGroup))
                          .ToList();
      return folders;
    }

    private DocModel GetFile(string filename)
    {
      filename = filename.Replace("|", "\\");
      DirectoryInfo di = new DirectoryInfo(documentationPath);
      FileInfo[] files = RecursiveFetch(4, di.FullName);
      var result = files.FirstOrDefault(x => x.FullName == filename);
      if (result == null) return new DocModel { content = filename };
      using (StreamReader streamReader = result.OpenText())
      {
        string s = "";
        s = streamReader.ReadToEnd();
        return new DocModel { content = s };
      }
    }
    private FolderModel BuildFolder(string key, IEnumerable<FileModel> fileGroup)
    {
      return new FolderModel { name = key, files = fileGroup.ToArray() };
    }

    private static FileModel BuildFileModel(FileInfo x, int trimLength)
    {
      var length = x.FullName.Count() - trimLength;
      var trimmedPath = x.FullName.Substring(trimLength, length).ToString();
      var splitPath = trimmedPath.Split('\\');
      return new FileModel
      {
        name = x.Name,
        path = x.FullName,
        trimmedPath = trimmedPath,
        createdDate = x.CreationTime,
        modifiedDate = x.LastWriteTime,
        pathParts =
        splitPath.TakeLast(4).ToArray(),
        pathPartsIsPartial =
        (splitPath.Count() > pathPartsMaxCount),
        pathPartCount = splitPath.Count()
      };
    }
    private FileInfo[] RecursiveFetch(int? depth, string path)
    {
      var currentDirectory = new DirectoryInfo(path);
      var currentFiles = currentDirectory.GetFiles("*.md");
      depth--;
      if (depth <= 0 && depth != null) return currentFiles;
      var children = Directory.GetDirectories(path).Where(x => x.Contains("node_modules") == false);
      foreach (var di in children)
      {
        FileInfo[] noFiles = { };
        var morefiles = RecursiveFetch(depth, di);
        currentFiles = currentFiles.Concat(morefiles).ToArray();
      }
      return currentFiles;
    }
  }
}