private void timer_Tick(object sender, EventArgs e)
{
// get node at mouse position
Point pt = PointToClient(Control.MousePosition);
TreeNode node = this.GetNodeAt(pt);
if (node == null)
{
return;
}
// if mouse is near to the top, scroll up
if (pt.Y < 30)
{
// set actual node to the upper one
if (node.PrevVisibleNode != null)
{
node = node.PrevVisibleNode;
// hide drag image
DragHelper.ImageList_DragShowNolock(false);
// scroll and refresh
node.EnsureVisible();
this.Refresh();
// show drag image
DragHelper.ImageList_DragShowNolock(true);
}
}
// if mouse is near to the bottom, scroll down
else if (pt.Y > this.Size.Height - 30)
{
if (node.NextVisibleNode != null)
{
node = node.NextVisibleNode;
DragHelper.ImageList_DragShowNolock(false);
node.EnsureVisible();
this.Refresh();
DragHelper.ImageList_DragShowNolock(true);
}
}
}
/// <summary>
/// 在将对象拖到控件的边界上发生。
/// </summary>
/// <param name="drgevent"></param>
protected override void OnDragOver(DragEventArgs e)
{
// Compute drag position and move image
Point formP = this.PointToClient(new Point(e.X, e.Y));
//DragHelper.ImageList_DragMove(formP.X - this.Left, formP.Y - this.Top);
DragHelper.ImageList_DragMove(formP.X, formP.Y);
// Get actual drop node
TreeNode dropNode = this.GetNodeAt(this.PointToClient(new Point(e.X, e.Y)));
if (dropNode == null)
{
e.Effect = DragDropEffects.None;
return;
}
e.Effect = DragDropEffects.Move;
// if mouse is on a new node select it
if (this._tempDropNode != dropNode)
{
DragHelper.ImageList_DragShowNolock(false);
this.SelectedNode = dropNode;
DragHelper.ImageList_DragShowNolock(true);
_tempDropNode = dropNode;
}
// Avoid that drop node is child of drag node
TreeNode tmpNode = dropNode;
while (tmpNode.Parent != null)
{
if (tmpNode.Parent == this._dragNode)
{
e.Effect = DragDropEffects.None;
}
tmpNode = tmpNode.Parent;
}
base.OnDragOver(e);
}