在Winfrom 中，如何实现combox 的列表自动显示ToolTip提示 ？

 

 1  //带ToolTip的combox类文件
 2  public class ComboBoxWithTooltip : ComboBox
 3     {
 4     //tipProperty为显示ToolTip文本的数据源的属性
 5         private string tipProperty;
 6         public string TipProperty
 7         {
 8             get { return tipProperty; }
 9             set
10             {
11                 if (tipProperty!=value)
12                 {
13                     tipProperty = value;
14                 }
15             }
16         }
17 
18        private ToolTip toolTipX = new ToolTip(); 
19     
20         /// <summary>
21         /// Initializes a new instance of the <see cref="ComboBoxWithTooltip"/> class.
22         /// </summary>
23         public ComboBoxWithTooltip()
24         {   
25             DrawMode = DrawMode.OwnerDrawFixed;
26         }
27 
28         /// <summary>
29         /// Raises the <see cref="E:System.Windows.Forms.ComboBox.DrawItem"/> event.
30         /// </summary>
31         /// <param name="e">A <see cref="T:System.Windows.Forms.DrawItemEventArgs"/> that contains the event data.</param>
32         protected override void OnDrawItem(DrawItemEventArgs e)
33         {
34              ; 
35 
36             // Needed gate when DropDownStyle set to DropDownList (thanks to "Andrew" remarking on my 
37             // StackOverflow post (stackoverflow.com/questions/680373/tooltip-for-each-items-in-a-combo-box/).
38             if (e.Index < 0) { return; }
39             string tiptext = FilterItemOnProperty(Items[e.Index], TipProperty) as string;//从数据源Items[e.Index]的 TipProperty属性获取ToolTip文本
40            string Itemtext = GetItemText(Items[e.Index]);
41             e.DrawBackground();
42             using (SolidBrush br = new SolidBrush(e.ForeColor))
43             { e.Graphics.DrawString(Itemtext, e.Font, br, e.Bounds); }
44             if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
45             {
46                 toolTipX.Show(tiptext, this, e.Bounds.Right, e.Bounds.Bottom);                
47                 //toolTip1.AutoPopDelay = 25000;
48                 //toolTip1.InitialDelay = 1000;
49                 //toolTip1.ReshowDelay = 0; 
50             }
51             e.DrawFocusRectangle();
52         }
53 
54         /// <summary>
55         /// Raises the <see cref="E:System.Windows.Forms.ComboBox.DropDownClosed"/> event.
56         /// </summary>
57         /// <param name="e">An <see cref="T:System.EventArgs"/> that contains the event data.</param>
58         protected override void OnDropDownClosed(EventArgs e)
59         {
60             toolTipX.Hide(this);
61             base.OnDropDownClosed(e);
62         }
63     }

 

 

===================================================

上边是实现后的结果，找了好长时间，才找到，做个记录。

实现代码如下：

ToolTip tt = null ;
       ComboBox cb = null ;
       private void Form1_Load( object sender, EventArgs e)
       {
           cb = new ComboBox();
           cb.Items.Insert(0, "第一" );
           cb.Items.Insert(1, "第二" );
           cb.Items.Insert(2, "第三" );
           cb.Items.Insert(3, "第四" );
           cb.DrawMode = DrawMode.OwnerDrawFixed;
           cb.DrawItem+= new DrawItemEventHandler(cb_DrawItem);
           cb.DropDownClosed+= new EventHandler(cb_DropDownClosed);
           this .Controls.Add(cb);
           cb.SelectedIndex = 1;
           tt = new ToolTip();
           tt.SetToolTip(cb, "zj" );
       }
void cb_DrawItem( object sender, System.Windows.Forms.DrawItemEventArgs e)
       {
           // 绘制背景
           e.DrawBackground();
           //绘制列表项目
           e.Graphics.DrawString(cb.Items[e.Index].ToString(), e.Font, System.Drawing.Brushes.Black, e.Bounds);
           //将高亮的列表项目的文字传递到toolTip1(之前建立ToolTip的一个实例)
           if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
               tt.Show(cb.Items[e.Index].ToString(), cb, e.Bounds.X + e.Bounds.Width, e.Bounds.Y + e.Bounds.Height);
           e.DrawFocusRectangle();
       }
       void cb_DropDownClosed( object sender, EventArgs e)
       {
           tt.Hide(cb);
       }