✅ Writing a dictionary to json file

public Dictionary<string, string> CheckForStyleFile(string username)
{
    StyleModel defaultStyle = new()
    {
        BackgroundColor = "#000000",
        BorderColor = "#24de45",
        FontColor = "#CDCDCD"
    };

    Dictionary<string, string> defaultDict = new();
    defaultDict.Add("background", defaultStyle.BackgroundColor);
    defaultDict.Add("border", defaultStyle.BorderColor);
    defaultDict.Add("font", defaultStyle.FontColor);

    try
    {
        if (!File.Exists(_stylesFile))
        {
            var data = JsonSerializer.Serialize(defaultDict);
            File.AppendAllText(_stylesFile, data);
            return defaultDict;
        }
        else
        {
            if (username.Length == 0)
            {
                return defaultDict;
            }
        }
    }
}

{
  "default": {
      "background": "#000000",
      "border": "#42fe45",
      "font": "#CDCDCD"
  }
}