/// <summary>
/// Determines the values of the following properties:
/// targetItemContainer, insertionIndex, and isInFirstHalf
/// </summary>
/// <remarks>
/// If the types of the dragged data and ItemsControl's source are compatible,
/// there are 3 situations to have into account when deciding the drop target:
/// 1. mouse is over an items container
/// 2. mouse is over the empty part of an ItemsControl, but ItemsControl is not empty
/// 3. mouse is over an empty ItemsControl.
/// The goal of this method is to decide on the values of the following properties:
/// targetItemContainer, insertionIndex and isInFirstHalf.
/// </remarks>
private void DecideDropTarget(DragEventArgs e)
{
int targetItemsControlCount = this.targetItemsControl.Items.Count;
object draggedItem = e.Data.GetData(this.format.Name);
if (IsDropDataTypeAllowed(draggedItem))
{
if (targetItemsControlCount > 0)
{
this.hasVerticalOrientation = DragDropUtilities.HasVerticalOrientation(this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(0) as FrameworkElement);
this.targetItemContainer = targetItemsControl.ContainerFromElement((DependencyObject)e.OriginalSource) as FrameworkElement;
if (this.targetItemContainer != null)
{
Point positionRelativeToItemContainer = e.GetPosition(this.targetItemContainer);
this.isInFirstHalf = DragDropUtilities.IsInFirstHalf(this.targetItemContainer, positionRelativeToItemContainer, this.hasVerticalOrientation);
this.insertionIndex = this.targetItemsControl.ItemContainerGenerator.IndexFromContainer(this.targetItemContainer);
if (!this.isInFirstHalf)
{
this.insertionIndex++;
}
}
else
{
this.targetItemContainer = this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(targetItemsControlCount - 1) as FrameworkElement;
this.isInFirstHalf = false;
this.insertionIndex = targetItemsControlCount;
}
}
else
{
this.targetItemContainer = null;
this.insertionIndex = 0;
}
}
else
{
this.targetItemContainer = null;
this.insertionIndex = -1;
e.Effects = DragDropEffects.None;
}
}
/// <summary>
/// Handles the PreviewDrop event of a DropTarget ItemsControl
/// </summary>
private void DropTarget_PreviewDrop(object sender, DragEventArgs e)
{
object draggedItem = e.Data.GetData(this.format.Name);
int indexRemoved = -1;
if (draggedItem != null)
{
if (this.sourceItemsControl != null)
{
if ((e.Effects & DragDropEffects.Move) != 0)
{
indexRemoved = DragDropUtilities.RemoveItemFromItemsControl(this.sourceItemsControl, draggedItem);
}
// This happens when we drag an item to a later position within the same ItemsControl.
if (indexRemoved != -1 && this.sourceItemsControl == this.targetItemsControl && indexRemoved < this.insertionIndex)
{
this.insertionIndex--;
}
}
DragDropUtilities.InsertItemInItemsControl(this.targetItemsControl, draggedItem, this.insertionIndex);
RemoveDraggedAdorner();
if (GetIsInsertionAdornerEnabled(sender as Visual))
{
RemoveInsertionAdorner();
}
var element = sender as FrameworkElement;
if (element != null)
{
var args = new OnDropEventArgs(OnDropEvent, e, draggedItem);
element.RaiseEvent(args);
}
}
e.Handled = true;
}