BrightIdeasSoftware.ObjectListView.MakeGroups C# (CSharp) Method

        protected virtual IList<OLVGroup> MakeGroups(GroupingParameters parms)
        {
            // There is a lot of overlap between this method and FastListGroupingStrategy.MakeGroups()
            // Any changes made here may need to be reflected there

            // Separate the list view items into groups, using the group key as the descrimanent
            NullableDictionary<object, List<OLVListItem>> map = new NullableDictionary<object, List<OLVListItem>>();
            foreach (OLVListItem olvi in parms.ListView.Items) {
                object key = parms.GroupByColumn.GetGroupKey(olvi.RowObject);
                if (!map.ContainsKey(key))
                    map[key] = new List<OLVListItem>();
                map[key].Add(olvi);
            }

            // Sort the items within each group (unless specifically turned off)
            OLVColumn sortColumn = parms.SortItemsByPrimaryColumn ? parms.ListView.GetColumn(0) : parms.PrimarySort;
            if (sortColumn != null && parms.PrimarySortOrder != SortOrder.None) {
                ColumnComparer itemSorter = new ColumnComparer(sortColumn, parms.PrimarySortOrder,
                    parms.SecondarySort, parms.SecondarySortOrder);
                foreach (object key in map.Keys) {
                    map[key].Sort(parms.ItemComparer ?? itemSorter);
                }
            }

            // Make a list of the required groups
            List<OLVGroup> groups = new List<OLVGroup>();
            foreach (object key in map.Keys) {
                string title = parms.GroupByColumn.ConvertGroupKeyToTitle(key);
                if (!String.IsNullOrEmpty(parms.TitleFormat)) {
                    int count = map[key].Count;
                    string format = (count == 1 ? parms.TitleSingularFormat : parms.TitleFormat);
                    try {
                        title = String.Format(format, title, count);
                    } catch (FormatException) {
                        title = "Invalid group format: " + format;
                    }
                }

                OLVGroup lvg = new OLVGroup(title);
                lvg.Collapsible = this.HasCollapsibleGroups;
                lvg.Key = key;
                lvg.SortValue = key as IComparable;
                lvg.Items = map[key];
                if (parms.GroupByColumn.GroupFormatter != null)
                    parms.GroupByColumn.GroupFormatter(lvg, parms);
                groups.Add(lvg);
            }

            // Sort the groups
            if (parms.GroupByOrder != SortOrder.None)
                groups.Sort(parms.GroupComparer ?? new OLVGroupComparer(parms.GroupByOrder));

            return groups;
        }