Tooltip Display Problem after postback

Hi,
 I write a code to Bind Dynamic Tooltip in DropDown.When First time Tooltip works Perfectly bind but when Postback occurs at  that time Tooltip does not Display.
Here is the Code
 
 private void BindDynamicTooltip(DropDownList cboDropdown)
    {
        for (int intCount = 0; intCount < cboDropdown.Items.Count; intCount++)
        {
            cboDropdown.Items[intCount].Attributes.Add("title", cboDropdown.Items[intCount].Text);
        }
    }
Please Help me
Thanks,
Viral Shah
 
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