我们如何在winui中获取父对象（calendarview）的子对象（calendardayitem）？

Question

In UWP,we can fetch the children by FindDescendants<>.But in winui, we can't able to do that. By doing with visualhelpertree,It always shows zero count in getchildCount() from the calendarview

I just wanted to know how to fetch the children of calendarview. Also i have tried this but shows me zero child always,

    private void FindDescendants1(DependencyObject parent, Type targetType)
        {
            int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
            itemchange.Text = childrenCount.ToString();
            for (int i = 0; i < childrenCount; i++)
            {
                var child =(CalendarViewDayItem) VisualTreeHelper.GetChild(parent, i);
                if (child.GetType() == targetType)
                {
                    results.Add(child);
                }
                FindDescendants1(child, targetType);
            }
        }

Simply I have created this function to get the child and called,

foreach (DependencyObject displayedDay in results)
        {
            //displayedDay = (CalendarViewDayItem)displayedDay;
            CalendarViewDayItem c = displayedDay as CalendarViewDayItem;
            if (_highlightedDates.Contains(c.Date))
            {
                Console.WriteLine(c.Date.ToString());
                //highlight
                c.Background = new SolidColorBrush(Colors.Red);
            }
            itemchange.Text = c.Date.ToString();
        }

But this not getting the child,results is the list of objects here where it always show me zero.

Answer 1

My first guess is that you are calling FindDescendants1() before the control is loaded, in the constructor for example. If your CalendarView is in a Page , try calling FindDescendants1() in the Page 's Loaded event.

But there's another problem in you code below.

var child = (CalendarViewDayItem)VisualTreeHelper.GetChild(parent, i);

You'll get an exception because you're trying to cast every DependencyObject to a CalendarViewDayItem . By removing the cast you should get the CalendarViewItems . Though, I would make the FinDescendants() static and just receive the results:

private static IEnumerable<T> FindDescendantsOfType<T>(DependencyObject parent) where T : DependencyObject
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(parent, i);
        
        if (child is T hit)
        {
            yield return hit;
        }

        foreach (T? grandChild in FindChildrenOfType<T>(child))
        {
            yield return grandChild;
        }
    }
}

And use it like this:

this.results = FindChildrenOfType<CalendarViewDayItem>(this.CalendarViewControl);

foreach (var item in this.results)
{
    // Do you work here...
}