private static void AttachDataGrid(DataGridControl grid, Action <VisibleItemsChangedEventArgs> changed)
{
RVSContext context = new RVSContext();
context.Callback = changed;
// To monitor collection changes
ICollectionView view = CollectionViewSource.GetDefaultView(grid.ItemsSource);
context.CollectionChangedHandler = delegate(object s, NotifyCollectionChangedEventArgs args)
{
DataGridControl_CollectionChanged(grid, args);
};
view.CollectionChanged += context.CollectionChangedHandler;
// To monitor scroll changes
ScrollViewer scroller = grid.Template.FindName("PART_ScrollViewer", grid) as ScrollViewer;
context.ScrollChangedHandler = delegate(object s, ScrollChangedEventArgs args)
{
DataGridControl_ScrollChanged(grid, args);
};
scroller.ScrollChanged += context.ScrollChangedHandler;
grid.SetValue(RVSContextProperty, context);
// First time notification
int start, end;
CalculateIndexRange(grid, out start, out end);
context.StartIndex = start;
context.EndIndex = end;
UpdateAndNotifyVisibleItems(grid);
}
private static void DataGridControl_CollectionChanged(DataGridControl grid,
NotifyCollectionChangedEventArgs e)
{
RVSContext context = grid.GetValue(RVSContextProperty) as RVSContext;
int firstIndex, lastIndex;
CalculateIndexRange(grid, out firstIndex, out lastIndex);
context.StartIndex = firstIndex;
context.EndIndex = lastIndex;
UpdateAndNotifyVisibleItems(grid);
}
private static void DetachDataGrid(DataGridControl grid)
{
RVSContext context = grid.GetValue(RVSContextProperty) as RVSContext;
ICollectionView view = CollectionViewSource.GetDefaultView(grid.ItemsSource);
view.CollectionChanged -= context.CollectionChangedHandler;
ScrollViewer scroller = grid.Template.FindName("PART_ScrollViewer", grid) as ScrollViewer;
scroller.ScrollChanged -= context.ScrollChangedHandler;
context.Callback = null;
grid.ClearValue(RVSContextProperty);
}
private static void UpdateAndNotifyVisibleItems(DataGridControl grid)
{
RVSContext context = grid.GetValue(RVSContextProperty) as RVSContext;
List <object> newItems = new List <object>();
List <object> oldItems = new List <object>();
List <object> unchangedItems = new List <object>();
for (int i = context.StartIndex; i <= context.EndIndex; i++)
{
object item = grid.Items[i];
if (context.VisibleItems.Contains(item))
{
context.VisibleItems.Remove(item);
unchangedItems.Add(item);
}
else
{
newItems.Add(item);
}
}
oldItems = context.VisibleItems;
context.VisibleItems = new List <object>(unchangedItems);
context.VisibleItems.AddRange(newItems);
if (oldItems.Count == 0 && newItems.Count == 0)
{
return; // No change
}
// Changes occurred, Notify
VisibleItemsChangedEventArgs args = new VisibleItemsChangedEventArgs()
{
AddedItems = newItems,
RemovedItems = oldItems
};
context.Callback(args);
}
