/// <summary>
        /// groups multiple Series into one according by MediaGroup
        /// </summary>
        private void GroupByMediaGroup()
        {
            List<Series> seriesCollection = this.ClonePerLanguage(this.SeriesCollection); /* original collection, cloned per language */
            List<Series> seriesCollectionPerMediaGroup = new List<Series>(); /* new collection of grouped series */
            List<Series> seriesCollectionWithoutMediaGroup = new List<Series>(); /* original series, used to remove old folders  */

            #region creating seriesListsPerMediaGroup
            string activeMediaGroup = string.Empty;
            List<Series> seriesListPerMediaGroup = new List<Series>();
            List<List<Series>> seriesListsPerMediaGroup = new List<List<Series>>();

            // creates new collection of lists of series, each latter one belongs to the same MediaGroup
            foreach (Series series in seriesCollection.OrderBy(o => o.MediaGroup).ThenBy(o => o.TitleSort).ToList())
            {
                seriesCollectionWithoutMediaGroup.Add(series);

                // create new Series, when a different MediaGroup is present
                if (series.MediaGroup != activeMediaGroup)
                {
                    // when new MediaGroup is found
                    // set new MediaGroup
                    activeMediaGroup = series.MediaGroup;

                    // create new series
                    seriesListPerMediaGroup = new List<Series>();
                    seriesListPerMediaGroup.Add(series);

                    // add list to new collection
                    seriesListsPerMediaGroup.Add(seriesListPerMediaGroup);
                }
                else
                {
                    // while finding series of same MediaGroup, adding those to seriesPerMediaGroup
                    seriesListPerMediaGroup.Add(series);
                }
            }
            #endregion

            // each first-level-List of seriesListsPerMediaGroup contains a series
            #region creating new Series with appropriate settings

            foreach (List<Series> seriesList in seriesListsPerMediaGroup)
            {
                if (seriesList.Count == 1)
                {
                    // adding directly, if only one series in MediaGroup
                    seriesCollectionPerMediaGroup.Add(seriesList[0]);
                }
                else
                {
                    // create new series per node in seriesListsPerMediaGroup
                    Series seriesPerMediaGroup = new Series(this.Configuration);
                    bool imagesContainsOneWithSeasonOne = false;
                    List<bool> seriesPerMediagroupContainsImageWithSeasonSpecial = new List<bool>();
                    List<bool> seriesPerMediagroupContainsImageWithSeasonAll = new List<bool>();

                    for (int i = 0; i < this.Configuration.NumberOfImageTypes; i++)
                    {
                        seriesPerMediagroupContainsImageWithSeasonSpecial.Add(false);
                        seriesPerMediagroupContainsImageWithSeasonAll.Add(false);
                    }

                    // set basic parameters for new Series, according to first member of MediaGroup
                    Series seriesBasicMember = seriesList[0];

                    seriesPerMediaGroup.Title = seriesBasicMember.MediaGroup;
                    seriesPerMediaGroup.TitleSort = seriesBasicMember.MediaGroup;
                    seriesPerMediaGroup.TitleOriginal = seriesBasicMember.MediaGroup;
                    seriesPerMediaGroup.MediaGroup = seriesBasicMember.MediaGroup;
                    seriesPerMediaGroup.Rating = seriesBasicMember.Rating;
                    seriesPerMediaGroup.PublishingYear = seriesBasicMember.PublishingYear;
                    seriesPerMediaGroup.PublishingDate = seriesBasicMember.PublishingDate;
                    seriesPerMediaGroup.RunTime = seriesBasicMember.RunTime;
                    seriesPerMediaGroup.MPAA = seriesBasicMember.MPAA;
                    seriesPerMediaGroup.PlayCount = seriesBasicMember.PlayCount;
                    seriesPerMediaGroup.PlayDate = seriesBasicMember.PlayDate;
                    seriesPerMediaGroup.IMDbId = seriesBasicMember.IMDbId;
                    seriesPerMediaGroup.Country = seriesBasicMember.Country;
                    seriesPerMediaGroup.Genres = seriesBasicMember.Genres;
                    seriesPerMediaGroup.Studios = seriesBasicMember.Studios;
                    seriesPerMediaGroup.VideoCodec = seriesBasicMember.VideoCodec;
                    seriesPerMediaGroup.VideoDefinition = seriesBasicMember.VideoDefinition;
                    seriesPerMediaGroup.VideoAspectRatio = seriesBasicMember.VideoAspectRatio;
                    seriesPerMediaGroup.AudioStreams = seriesBasicMember.AudioStreams;
                    seriesPerMediaGroup.SubTitles = seriesBasicMember.SubTitles;
                    seriesPerMediaGroup.MediaLanguages = seriesBasicMember.MediaLanguages;
                    seriesPerMediaGroup.NumberOfEpisodesPerSeason = new List<int>();
                    seriesPerMediaGroup.NumberOfEpisodesPerSeason.Add(0);

                    // adding basic images (without season) from seriesBasicMember
                    foreach (ImageFile imageFile in seriesBasicMember.Images)
                    {
                        if (imageFile.ImageType == Configuration.ImageType.CoverFront ||
                            imageFile.ImageType == Configuration.ImageType.CoverBack ||
                            imageFile.ImageType == Configuration.ImageType.Backdrop ||
                            imageFile.ImageType == Configuration.ImageType.Poster)
                        {
                            ImageFile imageFilePerMediaGroup = (ImageFile)imageFile.Clone();
                            imageFilePerMediaGroup.Media = seriesPerMediaGroup;

                            seriesPerMediaGroup.Images.Add(imageFilePerMediaGroup);
                        }
                    }

                    seriesPerMediaGroup.Content = "MediaCollection for " + seriesBasicMember.MediaGroup + " containing" + "\r\n" + "\r\n";

                    // adding each series to seriesPerMediaGroup
                    foreach (Series series in seriesList)
                    {
                        int fistSeasonInSeries = seriesPerMediaGroup.NumberOfEpisodesPerSeason.Count;

                        seriesPerMediaGroup.Content = seriesPerMediaGroup.Content + "Season " + fistSeasonInSeries.ToString() + ": " + series.Title + "\r\n";

                        // series based attributes
                        // checking if images of series contains one with Season 1
                        imagesContainsOneWithSeasonOne = false;
                        foreach (ImageFile imageContainsOneWithSeasonOne in series.Images)
                        {
                            if (imageContainsOneWithSeasonOne.Season == "1")
                            {
                                imagesContainsOneWithSeasonOne = true;
                                break;
                            }
                        }

                        foreach (ImageFile imageFile in series.Images)
                        {
                            ImageFile imageFilePerMediaGroup = (ImageFile)imageFile.Clone();
                            imageFilePerMediaGroup.Media = seriesPerMediaGroup;

                            // change type from basic image to season image
                            if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.Backdrop)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.SeasonBackdrop;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.CoverFront)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.SeasonCover;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.ExtraBackdrop)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.ExtraBackdrop;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.ExtraCover)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.ExtraCover;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.Poster)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.SeasonPoster;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.SeasonBackdrop)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.SeasonBackdrop;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.SeasonCover)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.SeasonCover;
                            }
                            else if (imageFilePerMediaGroup.ImageType == Configuration.ImageType.SeasonPoster)
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.SeasonPoster;
                            }
                            else
                            {
                                imageFilePerMediaGroup.ImageType = Configuration.ImageType.Unknown;
                            }

                            // exclude multiple special images for complete Series and Specials
                            if (imageFilePerMediaGroup.Season == string.Empty && !imagesContainsOneWithSeasonOne /* default images overruled by image per season */)
                            {
                                // setting Image without Season for first season
                                imageFilePerMediaGroup.Season = "1";
                            }
                            else if (imageFilePerMediaGroup.Season == "-1" && !seriesPerMediagroupContainsImageWithSeasonAll[(int)imageFilePerMediaGroup.ImageType] /* image for AllSeasons already added */)
                            {
                                seriesPerMediagroupContainsImageWithSeasonAll[(int)imageFilePerMediaGroup.ImageType] = true;
                            }
                            else if (imageFilePerMediaGroup.Season == "-1")
                            {
                                imageFilePerMediaGroup.Season = string.Empty;
                            }
                            else if (imageFilePerMediaGroup.Season == "0" && !seriesPerMediagroupContainsImageWithSeasonSpecial[(int)imageFilePerMediaGroup.ImageType] /* image for specials already added */)
                            {
                                seriesPerMediagroupContainsImageWithSeasonSpecial[(int)imageFilePerMediaGroup.ImageType] = true;
                            }
                            else if (imageFilePerMediaGroup.Season == "0")
                            {
                                imageFilePerMediaGroup.Season = string.Empty;
                            }

                            if (imageFilePerMediaGroup.Season == string.Empty)
                            {
                                // exclude multiple images for seasons
                                continue;
                            }
                            else if (imageFilePerMediaGroup.Season != "-1" && imageFilePerMediaGroup.Season != "0")
                            {
                                // Season for Specials ("0") and AllSeasons ("-1") stays unchanged
                                imageFilePerMediaGroup.Season = (int.Parse(imageFilePerMediaGroup.Season) + fistSeasonInSeries - 1).ToString();
                            }

                            if (imageFilePerMediaGroup.ImageType != Configuration.ImageType.Unknown)
                            {
                                seriesPerMediaGroup.Images.Add(imageFilePerMediaGroup);
                            }
                        }

                        // change Season for Actors accordingly
                        foreach (SeriesActor seriesActor in series.Actors)
                        {
                            for (int i = 0; i < seriesActor.Seasons.Count; i++)
                            {
                                if (seriesActor.Seasons[i] != string.Empty)
                                {
                                    seriesActor.Seasons[i] = (int.Parse(seriesActor.Seasons[i]) + fistSeasonInSeries - 1).ToString();
                                }
                            }
                        }

                        // add server to new series
                        seriesPerMediaGroup.AddServer(series.Server);

                        // episodes
                        foreach (Episode episode in series.Episodes)
                        {
                            Episode episodePerMediaGroup = (Episode)episode.Clone();
                            episodePerMediaGroup.Series = seriesPerMediaGroup;

                            // set new season and prepare NumberOfEpisodesPerSeason
                            episodePerMediaGroup.ActualSeason = episode.ActualSeason == "0" ? "0" : (int.Parse(episode.ActualSeason) + fistSeasonInSeries - 1).ToString();
                            episodePerMediaGroup.DisplaySeason = (int.Parse(episode.DisplaySeason) + fistSeasonInSeries - 1).ToString();
                            while (seriesPerMediaGroup.NumberOfEpisodesPerSeason.Count - 1 < (int)int.Parse(episodePerMediaGroup.ActualSeason))
                            {
                                seriesPerMediaGroup.NumberOfEpisodesPerSeason.Add(0);
                            }

                            seriesPerMediaGroup.NumberOfEpisodes = seriesPerMediaGroup.NumberOfEpisodes + (episode.IsSpecial ? 0 : 1);
                            seriesPerMediaGroup.NumberOfSpecials = seriesPerMediaGroup.NumberOfSpecials + (episode.IsSpecial ? 1 : 0);
                            seriesPerMediaGroup.NumberOfEpisodesPerSeason[(int)int.Parse(episodePerMediaGroup.ActualSeason)]++;

                            episodePerMediaGroup.ActualEpisode = (string)seriesPerMediaGroup.NumberOfEpisodesPerSeason.ElementAt((int)int.Parse(episodePerMediaGroup.ActualSeason)).ToString();
                            episodePerMediaGroup.DisplayEpisode = (string)(seriesPerMediaGroup.NumberOfSpecials + seriesPerMediaGroup.NumberOfEpisodes).ToString();

                            // // set plot - each content episode gets content from series, if empty
                            // if (!episodePerMediaGroup.IsSpecial && episodePerMediaGroup.Content == string.Empty)
                            // {
                            //     episodePerMediaGroup.Content = series.Content;
                            // }

                            // add series director, writer and actors to episodes within
                            episodePerMediaGroup.AddDirector(series.Directors);
                            episodePerMediaGroup.AddWriter(series.Writers);
                            episodePerMediaGroup.AddActor(series.Actors);

                            seriesPerMediaGroup.Episodes.Add(episodePerMediaGroup);
                        }
                    }

                    seriesPerMediaGroup.SetFilename();

                    seriesCollectionPerMediaGroup.Add(seriesPerMediaGroup);
                }
            }

            #endregion

            this.SeriesCollectionGroupedByMediaGroup = seriesCollectionPerMediaGroup;
            this.SeriesCollectionWithoutMediaGroup = seriesCollectionWithoutMediaGroup;
        }