BrightIdeasSoftware.VirtualObjectListView.GetPreviousItem C# (CSharp) Метод

        public override OLVListItem GetPreviousItem(OLVListItem itemToFind)
        {
            if (!this.ShowGroups)
                return base.GetPreviousItem(itemToFind);

            // Sanity
            if (this.OLVGroups == null || this.OLVGroups.Count == 0)
                return null;

            // If the given items is null, return the last member of the last group
            if (itemToFind == null) {
                OLVGroup lastGroup = this.OLVGroups[this.OLVGroups.Count - 1];
                return this.GetItem(this.GroupingStrategy.GetGroupMember(lastGroup, lastGroup.VirtualItemCount - 1));
            }

            // Find where this item occurs (which group and where in that group)
            int groupIndex = this.GroupingStrategy.GetGroup(itemToFind.Index);
            int indexWithinGroup = this.GroupingStrategy.GetIndexWithinGroup(this.OLVGroups[groupIndex], itemToFind.Index);

            // If it's not the first member of the group, just return the previous member
            if (indexWithinGroup > 0)
                return this.GetItem(this.GroupingStrategy.GetGroupMember(this.OLVGroups[groupIndex], indexWithinGroup - 1));

            // The item is the first member of its group. Return the last member of the previous group
            // (if there is one)
            if (groupIndex > 0) {
                OLVGroup previousGroup = this.OLVGroups[groupIndex - 1];
                return this.GetItem(this.GroupingStrategy.GetGroupMember(previousGroup, previousGroup.VirtualItemCount - 1));
            }

            return null;
        }