private static void RefreshVisibleItems(ScrollViewer scrollViewer)
{
ScrollBar verticalScrollBar =
FindChildren <ScrollBar>(scrollViewer).FirstOrDefault(s => s.Orientation == Orientation.Vertical);
if (verticalScrollBar != null)
{
PropertyDataGrid dataGrid = GetSenderDataGrid(scrollViewer);
int totalCount = dataGrid.Items.Count;
int firstVisible = (int)verticalScrollBar.Value;
int lastVisible = (int)(firstVisible + totalCount - verticalScrollBar.Maximum);
//List<Person> visiblePersons = new List<Person>();
List <object> visibleItems = new List <object>();
for (int i = firstVisible; i <= lastVisible; i++)
{
if (i < dataGrid.Items.Count)
{
visibleItems.Add(dataGrid.Items[i]);
}
}
SetVisibleItems(dataGrid, visibleItems);
CommandManager.InvalidateRequerySuggested();
}
}
private static void OnObserveVisibleItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
PropertyDataGrid dataGrid = d as PropertyDataGrid;
if (dataGrid == null)
{
return;
}
dataGrid.Loaded += DataGridLoaded;
}
private static void DataGridUnloaded(object sender, RoutedEventArgs e)
{
PropertyDataGrid dataGrid = (PropertyDataGrid)sender;
ScrollViewer scrollViewer = FindChildren <ScrollViewer>(dataGrid).FirstOrDefault();
if (scrollViewer != null)
{
scrollViewer.ScrollChanged -= ScrollViewerOnScrollChanged;
}
dataGrid.SizeChanged -= DataGridSizeChanged;
dataGrid.Unloaded -= DataGridUnloaded;
}
private static void DataGridLoaded(object sender, RoutedEventArgs routedEventArgs)
{
PropertyDataGrid dataGrid = (PropertyDataGrid)sender;
dataGrid.Loaded -= DataGridLoaded;
ScrollViewer scrollViewer = FindChildren <ScrollViewer>(dataGrid).FirstOrDefault();
if (scrollViewer != null)
{
SetSenderDataGrid(scrollViewer, dataGrid);
scrollViewer.ScrollChanged += ScrollViewerOnScrollChanged;
//ScrollViewerOnScrollChanged(scrollViewer, null);
RefreshVisibleItems(scrollViewer);
}
dataGrid.SizeChanged += DataGridSizeChanged;
dataGrid.Unloaded += DataGridUnloaded;
}
private static void SetSenderDataGrid(DependencyObject element, PropertyDataGrid value)
{
element.SetValue(SenderDataGridProperty, value);
}
