自定义控件并且加上JS

public class ufoTextBox : System.Web.UI.WebControls.TextBox
    {
        [TypeConverter(typeof(ufoTextBox)), DefaultValue(""), Category("Behavior")]
        public string SubmitControl
        {
            get
            {
                object ret = this.ViewState["SubmitControl"];
                if (ret != null)
                {
                    return (string)ret;
                }
                return string.Empty;
            }
            set
            {
                this.ViewState["SubmitControl"] = value;
            }
        }

        protected override void AddAttributesToRender(HtmlTextWriter writer)
        {
            base.AddAttributesToRender(writer);
            if (this.SubmitControl.Length > 0)
            {
                Control con = FindControl(SubmitControl);
                if (con != null)
                {
                    string script = "if(event.keyCode == 13){document.getElementById('" + con.ClientID + "').click();event.returnValue=false;}";
                    writer.AddAttribute("onkeydown", script);
                }
            }

        }
    }