/// <summary>Verifies that the dragged object is valid for dropping.
/// Occurs while the user is dragging an object over the <see cref="TreeView"/>.
/// May occur multiple times during a single drag.</summary>
void OnTreeDragOver(object sender, DragEventArgs e)
{
OnTreeDragEnter(sender, e);
if (e.Effect == DragDropEffects.None)
{
return;
}
TreeNode draggedNode = GetDraggedTreeNode(e);
Node dragged = Node.GetNode(draggedNode);
TreeNode targetNode = GetTargetNode(e);
if (targetNode == draggedNode)
{
e.Effect = DragDropEffects.None;
return;
}
Node target = Node.GetNode(targetNode);
if (dragged != target && target.AllowDrop && target.Accepts(dragged))
{// NOT same AND allows drops AND accepts the object
e.Effect = e.AllowedEffect;
if (previousTarget != null && previousTarget != targetNode)
{// target changed -> UN-highlight previous target
Highlight(previousTarget, false);
}
previousTarget = targetNode;
Highlight(targetNode);
}
else
{
e.Effect = DragDropEffects.None;
}
}
