khi nhấn enter sẽ chỏ tới đung nút cần nhấn

if (!IsPostBack)
{
   txtboxFirstName.Attributes.Add("onKeyPress", 
                   "doClick('" + btnSearch.ClientID + "',event)");

} 

<SCRIPT type=text/javascript>
    function doClick(buttonName,e)
    {
        //the purpose of this function is to allow the enter key to 
        //point to the correct button to click.
        var key;

         if(window.event)
              key = window.event.keyCode;     //IE
         else
              key = e.which;     //firefox
    
        if (key == 13)
        {
            //Get the button the user wants to have clicked
            var btn = document.getElementById(buttonName);
            if (btn != null)
            { //If we find the button click it
                btn.click();
                event.keyCode = 0
            }
        }
   }
</SCRIPT>