Change textbox's css class when ASP.NET Validation fails

How can I execute some javascript when a Required Field Validator attached to a textbox fails client-side validation? What I am trying to do is change the css class of the textbox, to make the textbox's border show red.

I am using webforms and I do have the jquery library available to me.



Here is quick and dirty thing (but it works!)

<form id="form1" runat="server">
      <asp:TextBox ID="txtOne" runat="server" />
      <asp:RequiredFieldValidator ID="rfv" runat="server" 
                                 ControlToValidate="txtOne" Text="SomeText 1" />
      <asp:TextBox ID="txtTwo" runat="server" />
      <asp:RequiredFieldValidator ID="rfv2" runat="server" 
                                 ControlToValidate="txtTwo" Text="SomeText 2" />
      <asp:Button ID="btnOne" runat="server" OnClientClick="return BtnClick();" 
                                         Text="Click" CausesValidation="true" />
    <script type="text/javascript">
        function BtnClick() {
            //var v1 = "#<%= rfv.ClientID %>";
            //var v2 = "#<%= rfv2.ClientID %>";
            var val = Page_ClientValidate();
            if (!val) {
                var i = 0;
                for (; i < Page_Validators.length; i++) {
                    if (!Page_Validators[i].isvalid) {
                        $("#" + Page_Validators[i].controltovalidate)
                         .css("background-color", "red");
            return val;

You could use the following script:


        if (typeof ValidatorUpdateDisplay != 'undefined') {
            var originalValidatorUpdateDisplay = ValidatorUpdateDisplay;

            ValidatorUpdateDisplay = function (val) {
                if (!val.isvalid) {
                    $("#" + val.controltovalidate).css("border", "2px solid red");



This code decorates the original ValidatorUpdateDisplay function responsible for updating the display of your validators, updating the controltovalidate as necessary.

Hope this helps,


I think you would want to use a Custom Validator and then use the ClientValidationFunction... Unless it helpfully adds a css class upon fail.


Some time ago I spend a few hours on it and since then I have been using some custom js magic to accomplish this.

In fact is quite simple and in the way that ASP.NET validation works. The basic idea is add a css class to attach a javascript event on each control you want quick visual feedback.

<script type="text/javascript" language="javascript">
    /* Color ASP NET validation */
    function validateColor(obj) {
         var valid = obj.Validators;
         var isValid = true;

         for (i in valid)
              if (!valid[i].isvalid)
                  isValid = false;

         if (!isValid)
             $(obj).addClass('novalid', 1000);
             $(obj).removeClass('novalid', 1000);

    $(document).ready(function() {
        $(".validateColor").change(function() {validateColor(this);});

For instance, that will be the code to add on an ASP.Net textbox control. Yes, you can put as many as you want and it will only imply add a CssClass value.

<asp:TextBox ID="txtBxEmail" runat="server" CssClass="validateColor" />

What it does is trigger ASP.Net client side validation when there is a change on working control and apply a css class if it's not valid. So to customize visualization you can rely on css.

.novalid {
    border: 2px solid #D00000;

It's not perfect but almost :) and at least your code won't suffer from extra stuff. And the best, works with all kind of Asp.Net validators, event custom ones.

I haven't seen something like this googling so I wan't to share my trick with you. Hope it helps.

extra stuff on server side:

After some time using this I also add this ".novalid" css class from code behind when need some particular validation on things that perhaps could be only checked on server side this way:

    if (!requiredFecha.IsValid || !CustomValidateFecha.IsValid)
        txtFecha.CssClass = "validateColor novalid";
        txtFecha.CssClass = "validateColor";

Here is my solution.

Advantages over other solutions:

  • Integrates seamlessly with ASP.NET - NO changes required to code. Just call the method on page load in a master page.
  • Automatically changes the CSS class when the text box or control changes


  • Uses some internal features of ASP.NET JavaScript code
  • Tested only on ASP.NET 4.0


  • Requires JQuery
  • Call the "Validation_Load" function when the page loads
  • Declare a "control_validation_error" CSS class

    function Validation_Load() {
    if (typeof (Page_Validators) != "object") {
    for (var i = 0; i < Page_Validators.length; i++) {
        var val = Page_Validators[i];
        var control = $("#" + val.controltovalidate);
        if (control.length > 0) {
            var tagName = control[0].tagName;
            if (tagName != "INPUT" && tagName != "TEXTAREA" && tagName != "SELECT") {
                // Validate sub controls
            else {
                // Validate the control
                control.change(function () {
                    var validators = this.Validators;
                    if (typeof (validators) == "object") {
                        var isvalid = true;
                        for (var k = 0; k < validators.length; k++) {
                            var val = validators[k];
                            if (val.isvalid != true) {
                                isvalid = false;
                        if (isvalid == true) {
                            // Clear the error
                        else {
                            // Show the error

Alternatively, just iterate through the page controls as follows: (needs a using System.Collections.Generic reference)

const string CSSCLASS = " error";    

protected static Control FindControlIterative(Control root, string id)
   Control ctl = root;
   LinkedList<Control> ctls = new LinkedList<Control>();
   while ( ctl != null )
     if ( ctl.ID == id ) return ctl;
     foreach ( Control child in ctl.Controls )
       if ( child.ID == id ) return child;
       if ( child.HasControls() ) ctls.AddLast(child);
     ctl = ctls.First.Value;
   return null;

protected void Page_PreRender(object sender, EventArgs e)
  //Add css classes to invalid items
  if ( Page.IsPostBack && !Page.IsValid )
    foreach ( BaseValidator item in Page.Validators )
       var ctrltoVal = (WebControl)FindControlIterative(Page.Form, item.ControlToValidate);
       if ( !item.IsValid ) ctrltoVal.CssClass += " N";
       else ctrltoVal.CssClass.Replace(" N", "");

Should work for most cases, and means you dont have to update it when you add validators. Ive added this code into a cstom Pageclass so it runs site wide on any page I have added validators to.


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