How to Add Tooltips to an ASP.NET Dropdownlist

A DropdownList can be enhanced with Tooltips for its items including the selected item.

Below is the codebehind for an ASP.NET Page with a DropdownList on it. Note that after the control is Databound, we add a title attribute for each item. We also add an onmouseover event for the selected item.


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace DropDownListToolTips
{
    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
             if (!IsPostBack)
            {
                 BindDdl();
             }
         }

        protected void BindDdl()
        {
           List<string> items = new List<string>();

             items.Add("One");
            items.Add("Two and a half");
            items.Add("Three");
            items.Add("Four");
            items.Add("One hundred Eighty Three");
            ddl1.DataSource = items;
             ddl1.DataBind();

             foreach (ListItem _listItem in this.ddl1.Items)
            {
                 _listItem.Attributes.Add("title", _listItem.Text);
            }

            // add a tooltip for the selected item also
            ddl1.Attributes.Add("onmouseover", "this.title=this.options[this.selectedIndex].title");
        }
     }
}