How can I display a Tool tip for a dropdownlist
The ToolTip property is inherited from the WebControl class and is not applicable to the DropDownList control. This implementation of the ToolTip property does not allow you to set a value and returns String. In a word, if we can make this (a dropdown with ToolTip) work with plain HTML and client side script, we should be able to emit the necessary code from ASP.NET.
More Details at DropDownList.ToolTip Property