public override void OnAttached()
{
if (AssociatedObject is IDragSource dragSource)
{
DragSource = dragSource;
DragSource.ItemsChanged += () =>
{
foreach (FrameworkElement item in DragSource.GetItems())
{
item.PreviewMouseLeftButtonDown -= Item_OnPreviewMouseLeftButtonDown;
item.PreviewMouseMove -= Item_OnPreviewMouseMove;
item.PreviewMouseLeftButtonDown += Item_OnPreviewMouseLeftButtonDown;
item.PreviewMouseMove += Item_OnPreviewMouseMove;
}
};
Background.PreviewMouseMove += Background_OnPreviewMouseMove;
Background.MouseLeftButtonUp += Background_OnMouseLeftButtonUp;
}
else
{
throw new ArgumentException("This behavior could be attached only to objects of type IDragSource");
}
}