根据textbox中的值，改变dropdownlist的选项

前台:

    function Select(txtId,ddlId) {
        function myFunc() {
            //alert(document.getElementById(txtId).value);
            //alert(document.getElementById(ddlId).value);
            var data = document.getElementById(txtId).value;
            var ddlgradelevel = document.getElementById(ddlId);
            for (var i = 0; i < ddlgradelevel.options.length; i++) {
                if (ddlgradelevel.options[i].text.indexOf(data) != -1) {
                    ddlgradelevel.options[i].selected = true;
                    break;
                }
            }
        }
        document.getElementById(txtId).attachEvent("onkeyup", myFunc);
    }

后台:

        protected void Page_Load(object sender, EventArgs e)
        {
              System.Web.UI.ScriptManager.RegisterStartupScript(TbGDZCHAO, GetType(), GetType().FullName,
"function a(){Select('" + TbGDZCHAO.ClientID + "','" + DropDownList3.ClientID + "');};setTimeout('a()',0);", true);
}