/// <summary>
/// Initializes a new instance of the DragInfo class.
/// </summary>
///
/// <param name="sender">
/// The sender of the mouse event that initiated the drag.
/// </param>
///
/// <param name="e">
/// The mouse event that initiated the drag.
/// </param>
public DragInfo(object sender, MouseButtonEventArgs e)
{
Effects = DragDropEffects.None;
MouseButton = e.ChangedButton;
VisualSource = sender as UIElement;
DragStartPosition = e.GetPosition(VisualSource);
DragDropCopyKeyState = DragDrop.GetDragDropCopyKeyState(VisualSource);
var dataFormat = DragDrop.GetDataFormat(VisualSource);
if (dataFormat != null)
{
DataFormat = dataFormat;
}
var sourceElement = e.OriginalSource as UIElement;
// If we can't cast object as a UIElement it might be a FrameworkContentElement, if so try and use its parent.
if (sourceElement == null && e.OriginalSource is FrameworkContentElement element)
{
sourceElement = element.Parent as UIElement;
}
if (sender is ItemsControl itemsControl)
{
SourceGroup = itemsControl.FindGroup(DragStartPosition);
VisualSourceFlowDirection = itemsControl.GetItemsPanelFlowDirection();
UIElement item = null;
if (sourceElement != null)
{
item = itemsControl.GetItemContainer(sourceElement);
}
if (item == null)
{
item = DragDrop.GetDragDirectlySelectedOnly(VisualSource) ? itemsControl.GetItemContainerAt(e.GetPosition(itemsControl)) : itemsControl.GetItemContainerAt(e.GetPosition(itemsControl), itemsControl.GetItemsPanelOrientation());
}
if (item != null)
{
// Remember the relative position of the item being dragged
PositionInDraggedItem = e.GetPosition(item);
var itemParent = ItemsControl.ItemsControlFromItemContainer(item);
if (itemParent != null)
{
SourceCollection = itemParent.ItemsSource ?? itemParent.Items;
if (itemParent != itemsControl)
{
if (item is TreeViewItem tvItem)
{
var tv = tvItem.GetVisualAncestor <TreeView>();
if (tv != null && !Equals(tv, itemsControl) && !tv.IsDragSource())
{
return;
}
}
else if (itemsControl.ItemContainerGenerator.IndexFromContainer(itemParent) < 0 && !itemParent.IsDragSource())
{
return;
}
}
SourceIndex = itemParent.ItemContainerGenerator.IndexFromContainer(item);
SourceItem = itemParent.ItemContainerGenerator.ItemFromContainer(item);
}
else
{
SourceIndex = -1;
}
var selectedItems = itemsControl.GetSelectedItems().OfType <object>().Where(i => i != CollectionView.NewItemPlaceholder).ToList();
SourceItems = selectedItems;
// Some controls (I'm looking at you TreeView!) haven't updated their
// SelectedItem by this point. Check to see if there 1 or less item in
// the SourceItems collection, and if so, override the control's SelectedItems with the clicked item.
//
// The control has still the old selected items at the mouse down event, so we should check this and give only the real selected item to the user.
if (selectedItems.Count <= 1 || SourceItem != null && !selectedItems.Contains(SourceItem))
{
SourceItems = Enumerable.Repeat(SourceItem, 1);
}
VisualSourceItem = item;
}
else
{
SourceCollection = itemsControl.ItemsSource ?? itemsControl.Items;
}
}
else
{
SourceItem = (sender as FrameworkElement)?.DataContext;
if (SourceItem != null)
{
SourceItems = Enumerable.Repeat(SourceItem, 1);
}
VisualSourceItem = sourceElement;
PositionInDraggedItem = sourceElement != null?e.GetPosition(sourceElement) : DragStartPosition;
}
if (SourceItems == null)
{
SourceItems = Enumerable.Empty <object>();
}
}
