How to display different tooltip on ListBox items in listbox item tooltip
ListBox is an list web server control. listbox server control allow us to select a single item or multiple items at a time. listbox ToolTip property allow us to get or set a text to display when the mouse pointer hover over the listbox server control.

but listbox has no built in property to display tooltip for individual item. we can do this by applying few techniques. listbox ListItem object have a property name Attributes. we can apply many attributes (css style) to individual list item by adding attribute to the individual ListItem object. ListItem Attributes property Add() method allow us to add attribute to the specified list item.

ListItem 'title' attribute and its value allow us to display tooltip on the item when user mouse hover over the specified item. so we loop through the listbox items collection and add title attribute to its item's attributes collection. finally listbox control display different tooltip for its different item. we applied item text to display as tooltip.

the following c# example code demonstrate us how can we display tooltip for listbox individual items in an application.

<%@ Page Language="C#" AutoEventWireup="true"%>    
<!DOCTYPE html>
<script runat="server">  
    protected void Page_Load(object sender, EventArgs e)  
        foreach(ListItem li in ListBox1.Items)
            string tip = li.Text + " | " + li.Value;
            li.Attributes.Add("title", tip);
<html xmlns="">        
<head id="Head1" runat="server">        
    <title> listbox item tooltip</title>  
    <form id="form1" runat="server">        
        <h2 style="color:MidnightBlue; font-style:italic;">        
   example - listbox item tooltip
        <hr width="550" align="left" color="Gainsboro" />   
        <br />     
            Font-Names="Comic Sans MS"  
            <asp:ListItem Text="Guianan Piculet" Value="1"></asp:ListItem>
            <asp:ListItem Text="Rufous Piculet" Value="2"></asp:ListItem>
            <asp:ListItem Text="Acorn Woodpecker" Value="3"></asp:ListItem>
            <asp:ListItem Text="Red-headed Woodpecker" Value="4"></asp:ListItem>
            <asp:ListItem Text="Yellow-fronted Woodpecker" Value="5"></asp:ListItem>
More examples