// playyuer@Microshaoft.com invent
//一个 TreeView 的派生类: TreeViewEx 实现 NodeShowToolTip、NodeDoubleClick 事件
//1.实现了 NodeShowToolTip 事件,结合键盘 Ctrl 键显示及设置 ToolTipText
//2.实现了 NodeDoubleClick 事件,可在调用中只响应"叶子"节点
//3.点击 TreeView 空白处不选中任何节点
//Class1.cs
using System;
public class TreeViewEx : System.Windows.Forms.TreeView
{
    public event TreeViewExEventHandler NodeDoubleClick;
    public event TreeViewExEventHandler NodeShowToolTip;
    private void OnNodeDoubleClick(System.Windows.Forms.TreeNode xx)
    {
        if(this.NodeDoubleClick != null)
        {
            this.NodeDoubleClick(this,new TreeViewExEventArgs(xx));
        }
    }
    private void OnNodeShowToolTip(System.Windows.Forms.TreeNode xx, System.Windows.Forms.ToolTip yy)
    {
        if(this.NodeShowToolTip != null)
        {
            if ((xx != null) && (this.toolTip !=null))
                this.NodeShowToolTip(this,new TreeViewExEventArgs(xx,this.toolTip));
        }
    }
    protected override void OnDoubleClick(System.EventArgs e)
    {
        if (this.SelectedNode != null)
            this.OnNodeDoubleClick(this.SelectedNode);
        base.OnDoubleClick(e);
    }
    private System.Windows.Forms.ToolTip toolTip;
    public TreeViewEx()
    {
        toolTip = new System.Windows.Forms.ToolTip();
        this.toolTip.InitialDelay = 300;
        this.toolTip.ReshowDelay = 0;
    }
    protected override void OnClick (System.EventArgs e)
    {
        if (this.GetNodeAt(System.Windows.Forms.TreeView.MousePosition.X,System.Windows.Forms.TreeView.MousePosition.Y) == null)
            this.SelectedNode = null;
        base.OnClick(e);
    }
    protected override void OnMouseDown (System.Windows.Forms.MouseEventArgs e)
    {
        if (this.GetNodeAt(e.X,e.Y) == null)
            this.SelectedNode = null;
        base.OnMouseDown(e);

    }
    private System.Windows.Forms.TreeNode LastTreeNode;
    protected override void OnMouseMove (System.Windows.Forms.MouseEventArgs e)
    {
        this.Cursor = System.Windows.Forms.Cursors.Default ;
        System.Windows.Forms.TreeNode treeNode;
        treeNode = this.GetNodeAt(e.X,e.Y) ;
      &nbs