How to Preserve the Groups Expand State When New Item is Added

Environment

Product Version	2019.1.220
Product	RadTimeline for WPF

Description

How to preserve groups' collapsed/expanded state when new items are added to the RadTimeline.

Solution

Save the names of the TimelineItemGroupControl elements.

C#

	public partial class MainWindow : Window
    {
        private ObservableCollection<MyPlotInfo> source;        
        private List<string> expandedGroupNames = new List<string>();
        
        public MainWindow()
        {
            InitializeComponent();            
            this.source = new ObservableCollection<MyPlotInfo>();
        }        

        private void AddNewDataItem(DateTime start, TimeSpan duration, string groupName)
        {
            this.PreserveExpandedGroups();
            this.source.Add(new MyPlotInfo()
            {
                Start = start,
                Duration = duration,
                GroupName = groupName
            });
            this.RestorePreservedGroups();
        }
        
        private void PreserveExpandedGroups()
        {
            this.expandedGroupNames.Clear();

            foreach (var group in this.timeline.GroupedDataItems)
            {                
                var groupContainer = this.timeline.GetGroupByGroupHeader(group.GroupKey);
                if (groupContainer != null && groupContainer.IsExpanded)
                {
                    this.expandedGroupNames.Add(group.GroupKey);
                }
            }
        }

        private void RestorePreservedGroups()
        {
            foreach (var groupName in this.expandedGroupNames)
            {
                var groupContainer = this.timeline.GetGroupByGroupHeader(groupName);
                if (groupContainer != null)
                {
                    groupContainer.IsExpanded = true;
                }                
            }
        }
    }

Note that the code snippet is not fully functional. You will need to add a logic that populates the source and also that calls the AddNewDataItem method.

See Also

• Grouping