c# – 使用拖放方式时,是否可以使TreeView展开用户悬停的节点？

您可以使用DragOver事件;当您拖动对象时,它会反复触发
延迟后打开可以非常容易地使用两个额外的变量来记录鼠标下的最后一个对象和时间.不需要线程或其他技巧(在我的例子中,lastDragDestination和lastDragDestinationTime)

从我自己的代码：

TreeNode lastDragDestination = null;
DateTime lastDragDestinationTime;

private void tvManager_DragOver(object sender,DragEventArgs e)
{
    IconObject dragDropObject = null;
    TreeNode dragDropNode = null;

    //always disallow by default
    e.Effect = DragDropEffects.None;

    //make sure we have data to transfer
    if (e.Data.GetDataPresent(typeof(TreeNode)))
    {
        dragDropNode = (TreeNode)e.Data.GetData(typeof(TreeNode));
        dragDropObject = (IconObject)dragDropNode.Tag;
    }
    else if (e.Data.GetDataPresent(typeof(ListViewItem)))
    {
        ListViewItem temp (ListViewItem)e.Data.GetData(typeof(ListViewItem));
        dragDropObject = (IconObject)temp.Tag;
    }

    if (dragDropObject != null)
    {
        TreeNode destinationNode = null;
        //get current location
        Point pt = new Point(e.X,e.Y);
        pt = tvManager.PointToClient(pt);
        destinationNode = tvManager.GetNodeAt(pt);
        if (destinationNode == null)
        {
            return;
        }

        //if we are on a new object,reset our timer
        //otherwise check to see if enough time has passed and expand the destination node
        if (destinationNode != lastDragDestination)
        {
            lastDragDestination = destinationNode;
            lastDragDestinationTime = DateTime.Now;
        }
        else
        {
            TimeSpan hoverTime = DateTime.Now.Subtract(lastDragDestinationTime);
            if (hoverTime.TotalSeconds > 2)
            {
                destinationNode.Expand();
            }
        }
    }
}