Dropdown tooltip for C#.NET

In th PreRender event of the dropdownlist you can do this

protected void ddlDropDown_PreRender(object sender, EventArgs e)
{
       ddlDropDown.Attributes.Add("ToolTip", "Please select an item from the list");
}
   

Hi Vickram,

Thank you for your response. Would you please let me know how to write the code if I would like to display the tooltip using variable and the values might be different. From your example above, the tooltip is hardcoded. Please advice.

Thanks,
Chew

I found this code somewhere. Anyone know how to convert it to web control?

//Code Start
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;

namespace ListBoxToolTips
{
      /// <summary>
      ///
      /// </summary>
      public class ToolTipListBox : System.Windows.Forms.ListBox
      {
            [StructLayout(LayoutKind.Sequential)]
            public struct SIZE
            {
                  public int cx;
                  public int cy;
            }
            [DllImport("gdi32.dll")]
            public static extern int GetTextExtentPoint32(IntPtr hdc,
                  String str, int len, ref SIZE size);

            [DllImport("user32.dll")]
            public static extern IntPtr GetDC(IntPtr hWnd);

            [DllImport("user32.dll")]
            public static extern int ReleaseDC(IntPtr hWnd,IntPtr hdc);


            public ToolTipListBox()
            {                  
                  tp.InitialDelay = 500;
                  tp.ReshowDelay = 500;
                  tp.AutoPopDelay = 3000;                  
                  tp.Active = true;                  
            }      

            
            protected override void OnMouseMove(System.Windows.Forms.MouseEventArgs e)
            {                        
                  int index = IndexFromPoint(e.X,e.Y);
                  if(index != ListBox.NoMatches )
                  {                        
                        if( LastIndex != index )
                        {
                              string s = Items[index].ToString();      

                              IntPtr hdc = GetDC(this.Handle);
                              SIZE size;
                              size.cx = 0;
                              size.cy = 0;
                              GetTextExtentPoint32(hdc,s,s.Length,ref size);
                              ReleaseDC(this.Handle,hdc);

                              if(this.Width < size.cx)                              
                                    tp.SetToolTip(this,s);

                              LastIndex = index;                        
                        }                                          
                  }
            }
            
            private ToolTip tp = new ToolTip();
            private int LastIndex = -1;
            
      }
}
//Code End

Please help.
Thanks,
Chew