RadGridView WPF always expands when updating the ItemsSource

[Andreea]

Hi,

I have a RadGridView in WPF where I use CustomGrouping for displaying it as a hierarchical structure. I set on it AutoExpandGroups="True" in order to be expanded by default. My problem is, if I manually collapse something in the RadGridView and I make an update to the list bounded to ItemsSource, the RadGridView automatically expands and does not stay as it was.

Thanks

[Andreea]

This is the closest I could get but it still does not work.

private Dictionary<object, GroupHeaderRow> groupRowMapping = new Dictionary<object, GroupHeaderRow>();
private List<object> collapsedGroupKeys = new List<object>();

private void radGridView_Loaded(object sender, RoutedEventArgs e)
{
    ReloadData();
}

private void radGridView_OnGroupRowIsExpandedChanged(object sender, GroupRowEventArgs e)
{
    if (!(e.Row is GroupHeaderRow groupHeaderRow))
        return;

    var groupKey = DetermineGroupKey(groupHeaderRow);

    if (groupKey != null)
    {
        if (!groupHeaderRow.IsExpanded)
        {
            collapsedGroupKeys.Add(groupKey);
        }
        else
        {
            collapsedGroupKeys.Remove(groupKey);
        }
    }
}
private object DetermineGroupKey(GroupHeaderRow groupHeaderRow)
{
    return groupHeaderRow.DataContext; 
}

private void ReloadData()
{
    PopulateGroupRowMapping();
    RestoreCollapsedState();
}

private void RestoreCollapsedState()
{
    foreach (var groupRowKey in collapsedGroupKeys)
    {
        if (groupRowMapping.ContainsKey(groupRowKey))
        {
            var groupRow = groupRowMapping[groupRowKey];
            groupRow.IsExpanded = false;
        }
    }
}

private void PopulateGroupRowMapping()
{
    groupRowMapping.Clear();
    if (radGridView.Items.Groups != null)
    {
        foreach (var groupRow in radGridView.Items.Groups)
        {
            if (groupRow is CollectionViewGroup collectionViewGroup)
            {
                foreach (var item in collectionViewGroup.Items)
                {
                    if (item is GroupHeaderRow headerRow)
                    {
                        var groupKey = DetermineGroupKey(headerRow);
                        if (groupKey != null && !groupRowMapping.ContainsKey(groupKey))
                        {
                            groupRowMapping[groupKey] = headerRow;
                        }
                    }
                }
            }
        }
    }
}

[Martin Ivanov]

Hello Andreea,

If you make an update in the existing list assigned to the ItemsSource the groups should not change their expand state. Do you mean that you reset the ItemsSource property? If that is the case, then you can consider only removing and adding items from the existing collection instance. Otherwise, you will need to cache the IsExpanded state of the groups and restore it manually similar to what you do in your custom code with the "groupRowMapping" dictionary.

Regards,
Martin Ivanov
Progress Telerik

[Andreea]

Thank you, Martin!

Yes, I cached the IsExpanded state.