System.ArgumentException: 'Illegal characters in path.'

[TuDo1403]

private async void DownloadSelectedRowAudio(int rowIndex)
        {
            var selectedUrl = videos[rowIndex].Url;
            var client = new YoutubeClient();
            var streamInfoSet = await client.GetVideoMediaStreamInfosAsync(YoutubeClient.ParseVideoId(selectedUrl));
            var streamInfo = streamInfoSet.Audio.OrderByDescending(a => a.Bitrate).First();
            var extension = streamInfo.Container;
            await client.DownloadMediaStreamAsync(streamInfo, $"C:\\Users\\{System.Environment.UserName}\\Desktop\\{videos[rowIndex].Title.Trim()}.{extension}");
        }

[TuDo1403]

public static string RemoveIllegalChars(this string source)
        {
            return string.Join("_", source.Split(Path.GetInvalidFileNameChars()));
        }