/// <summary>
/// Returns data as a SelectionCollection.
/// </summary>
/// <param name="data">The data object.</param>
/// <returns>A selection collection.</returns>
internal static SelectionCollection ToSelectionCollection(object data)
{
//------------------------
// The purpose of this method is to wrap data into a "Selection" class
// (unless it is already a Selection), and then put the Selection
// into a SelectionCollection (unless it is already a SelectionCollection).
//------------------------
if (data == null)
{
return(new SelectionCollection());
}
SelectionCollection selectionCollection = data as SelectionCollection;
if (selectionCollection == null)
{
selectionCollection = new SelectionCollection();
Selection selection = data as Selection;
if (selection == null)
{
selection = new Selection(data);
}
selectionCollection.Add(selection);
}
return(selectionCollection);
}
/// <summary>
/// Adds all selected items when drag operation begins.
/// </summary>
/// <param name="eventArgs">Information about the event.</param>
protected override void OnItemDragStarting(ItemDragEventArgs eventArgs)
{
SelectionCollection selectionCollection = new SelectionCollection();
// If panel is virtualized there is no way of knowing the precise
// index of each selected item.
Panel itemsHost = this.ListBox.GetItemsHost();
if (itemsHost is VirtualizingPanel)
{
foreach (object item in this.ListBox.SelectedItems)
{
selectionCollection.Add(new Selection(item));
}
// Adding the item dragged even if it isn't selected
SelectionCollection defaultSelectionCollection = SelectionCollection.ToSelectionCollection(eventArgs.Data);
if (defaultSelectionCollection.Count == 1 && !selectionCollection.Any(selection => object.Equals(selection.Item, defaultSelectionCollection[0].Item)))
{
selectionCollection.Add(defaultSelectionCollection[0]);
}
}
else
{
for (int cnt = 0; cnt < this.ListBox.Items.Count; cnt++)
{
ListBoxItem listBoxItem = this.ListBox.ItemContainerGenerator.ContainerFromIndex(cnt) as ListBoxItem;
if (listBoxItem.IsSelected)
{
selectionCollection.Add(new Selection(cnt, this.ListBox.Items[cnt]));
}
}
// Adding the item dragged even if it isn't selected
SelectionCollection defaultSelectionCollection = GetSelectionCollection(eventArgs.Data);
if (defaultSelectionCollection.Count == 1)
{
if (selectionCollection.All(selection => selection.Index != defaultSelectionCollection[0].Index))
{
selectionCollection.Add(defaultSelectionCollection[0]);
}
}
}
eventArgs.Data = selectionCollection;
CardPanel cardPanel = new CardPanel();
IEnumerable <UIElement> itemContainers =
selectionCollection.SelectedItems
.Select(item => this.ListBox.ItemContainerGenerator.ContainerFromItem(item))
.Where(item => item != null)
.OfType <UIElement>();
foreach (ListBoxItem row in itemContainers)
{
cardPanel.Children.Add(new Image {
Source = new WriteableBitmap(row, new TranslateTransform())
});
}
eventArgs.DragDecoratorContent = cardPanel;
eventArgs.Handled = true;
base.OnItemDragStarting(eventArgs);
}