如何在单个treeview中实现拖放？

Question

    如何在treewview 中 拖放， 在放的时候，放的那个节点不知道给如何确定？ 

Answer 1

 #region TreeView Drag/Drop
// Constants for the SendMessage() method.
        private const int WM_HSCROLL = 276;
        private const int WM_VSCROLL = 277;
        private const int SB_LEFT = 6;
        private const int SB_RIGHT = 7;
        private const int SB_TOP = 6;
        private const int SB_BOTTOM = 7;
        [DllImport("user32.dll")]
        private static extern int SendMessage(IntPtr hWnd, int wMsg,
                                          int wParam, int lParam);        // Node being dragged
        private TreeNode dragNode = null;
        // Temporary drop node for selection
        private TreeNode tempDropNode = null;        private void treeView_DragDrop(object sender, DragEventArgs e)
        {
            // Unlock updates
            DragHelper.ImageList_DragLeave(this.treeView.Handle);            // Get drop node
            TreeNode dropNode = this.treeView.GetNodeAt(this.treeView.PointToClient(new Point(e.X, e.Y)));            // If drop node isn't equal to drag node, add drag node as child of drop node
            if (this.dragNode != dropNode)
            {
                // Remove drag node from parent
                if (this.dragNode.Parent == null)
                {
                    this.treeView.Nodes.Remove(this.dragNode);
                }
                else
                {
                    this.dragNode.Parent.Nodes.Remove(this.dragNode);
                }                // Add drag node to drop node
                dropNode.Nodes.Add(this.dragNode);
                dropNode.ExpandAll();                // Set drag node to null
                this.dragNode = null;
            }
        }        private void treeView_DragEnter(object sender, DragEventArgs e)
        {
            DragHelper.ImageList_DragEnter(this.treeView.Handle, e.X - this.treeView.Left,
                e.Y - this.treeView.Top);
        }        private void treeView_DragLeave(object sender, EventArgs e)
        {
            DragHelper.ImageList_DragLeave(this.treeView.Handle);
        }        private void treeView_DragOver(object sender, DragEventArgs e)
        {
            // Compute drag position and move image
            Point formP = this.PointToClient(new Point(e.X, e.Y));
            DragHelper.ImageList_DragMove(formP.X - this.treeView.Left, formP.Y - this.treeView.Top);            // Get actual drop node
            TreeNode dropNode = this.treeView.GetNodeAt(this.treeView.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.treeView.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;
            }            Point pt = this.treeView.PointToClient(new Point(e.X, e.Y));
            // if mouse is near to the top, scroll up
            if (pt.Y < 30)
            {
                // set actual node to the upper one
                if (dropNode.PrevVisibleNode != null)
                {
                    dropNode = dropNode.PrevVisibleNode;                    // hide drag image
                    DragHelper.ImageList_DragShowNolock(false);                    SendMessage(treeView.Handle, WM_VSCROLL, SB_TOP, 0);                    // show drag image
                    DragHelper.ImageList_DragShowNolock(true);                }
            }
            // if mouse is near to the bottom, scroll down
            else if (pt.Y > this.treeView.Size.Height - 30)
            {
                if (dropNode.NextVisibleNode != null)
                {
                    dropNode = dropNode.NextVisibleNode;                    DragHelper.ImageList_DragShowNolock(false);                    SendMessage(treeView.Handle, WM_VSCROLL, SB_BOTTOM, 0);                    DragHelper.ImageList_DragShowNolock(true);
                }
            }
            // if mouse is near to the left, scroll left
            else if (pt.X < 30)
            {
                //dropNode = dropNode.NextVisibleNode;                DragHelper.ImageList_DragShowNolock(false);                SendMessage(treeView.Handle, WM_HSCROLL, SB_LEFT, 0);                DragHelper.ImageList_DragShowNolock(true);
            }
            // if mouse is near to the right, scroll right
            else if (pt.X > this.treeView.Size.Width - 30)
            {
                //dropNode = dropNode.NextVisibleNode;                DragHelper.ImageList_DragShowNolock(false);                SendMessage(treeView.Handle, WM_HSCROLL, SB_RIGHT, 0);                DragHelper.ImageList_DragShowNolock(true);
            }
        }        private void treeView_GiveFeedback(object sender, GiveFeedbackEventArgs e)
        {
            if (e.Effect == DragDropEffects.Move)
            {
                // Show pointer cursor while dragging
                e.UseDefaultCursors = false;
                this.treeView.Cursor = Cursors.Default;
            }
            else e.UseDefaultCursors = true;
        }        private void treeView_ItemDrag(object sender, ItemDragEventArgs e)
        {
            // Get drag node and select it
            this.dragNode = (TreeNode)e.Item;
            this.treeView.SelectedNode = this.dragNode;            // Reset image list used for drag image
            this.imageListDrag.Images.Clear();
            this.imageListDrag.ImageSize = new Size(this.dragNode.Bounds.Size.Width + this.treeView.Indent, this.dragNode.Bounds.Height);            // Create new bitmap
            // This bitmap will contain the tree node image to be dragged
            Bitmap bmp = new Bitmap(this.dragNode.Bounds.Width + this.treeView.Indent, this.dragNode.Bounds.Height);            // Get graphics from bitmap
            Graphics gfx = Graphics.FromImage(bmp);            // Draw node icon into the bitmap
            gfx.DrawImage(this.imageListTreeView.Images[dragNode.ImageIndex], 0, 0);            // Draw node label into bitmap
            gfx.DrawString(this.dragNode.Text,
                this.treeView.Font,
                new SolidBrush(this.treeView.ForeColor),
                (float)this.treeView.Indent, 1.0f);            // Add bitmap to imagelist
            this.imageListDrag.Images.Add(bmp);            // Get mouse position in client coordinates
            Point p = this.treeView.PointToClient(Control.MousePosition);            // Compute delta between mouse position and node bounds
            int dx = p.X + this.treeView.Indent - this.dragNode.Bounds.Left;
            int dy = p.Y - this.dragNode.Bounds.Top;            // Begin dragging image
            if (DragHelper.ImageList_BeginDrag(this.imageListDrag.Handle, 0, dx, dy))
            {
                // Begin dragging
                this.treeView.DoDragDrop(bmp, DragDropEffects.Move);
                // End dragging image
                DragHelper.ImageList_EndDrag();
            }
        }
        #endregion

Answer 2

#region TreeView拖动
        private void tvFormel_ItemDrag(object sender, ItemDragEventArgs e)
        {
            TreeNode tn = e.Item as TreeNode;
            //根节点不允许拖放操作
            if ((e.Button == MouseButtons.Left) && (tn != null) && (tn.Parent != null)) 
            {
                this.tvFormel.DoDragDrop(tn, DragDropEffects.Copy | DragDropEffects.Move | DragDropEffects.Link);
            }
            //DoDragDrop(e.Item, DragDropEffects.Move);
        }        private void tvFormel_DragEnter(object sender, DragEventArgs e)
        {
             if (e.Data.GetDataPresent("System.Windows.Forms.TreeNode"))
            {
                e.Effect = DragDropEffects.Move;
            }
            else
            {
                e.Effect = DragDropEffects.None;
            }
        }        private void tvFormel_DragDrop(object sender, DragEventArgs e)
        {
            TreeNode NewNode;
            if (e.Data.GetDataPresent(typeof(TreeNode)))
            {
                Point pt = ((TreeView)sender).PointToClient(new Point(e.X, e.Y));                TreeNode DestinationNode = ((TreeView)sender).GetNodeAt(pt);                NewNode = (TreeNode)e.Data.GetData("System.Windows.Forms.TreeNode");                DestinationNode.Nodes.Add((TreeNode)NewNode.Clone());                DestinationNode.Expand();                //删除已经移动的节点
                NewNode.Remove();            }
        }
        #endregion