ICodeFactory Labs

Dynamically adding ASP.NET validators and ASP.NET ajax validation callout extenders using Javascript

by Lacio 13. May 2010 01:33

Have you ever encountered a problem where you generated some content dynamically without the help of the server and server side code, but still needed to perform some basic validation on those contents?

That is exactly what this post deals with – validating content which is taken from dynamically generated input fields and adding the validation callout extender to it. 

Since I did not find any suitable solutions online, I decided to do it myself. Turned out the solution is not so hard at all, and after a small analysis on the page source of pages with regular validation, I got an idea on how to do it.

The first thing to notice is that after the aspx page is parsed, the output of a validator control (of any type) is a SPAN tag. Sort of. The tag has some unconventional attributes, off course depending on the type of the validator used, but we will get to that later. Besides this, a reference to the span is kept in an array called Page_Validators, which is an array consisting of all the validators present on the page.

So let’s go step by step.

First create the span tag and place it in the DOM where you would place the validator control. Lets say we have an input field and we place a RequiredFieldValidator next to it, like in the code below:


               // Get the table:
                var tblEditItems = $get('tblEditItems');
                // Get the number of rows currently in the table:
                var rowsCount = tblEditItems.rows.length;
                // Insert a new row at the end of the table:
                var row = tblEditItems.insertRow(rowsCount);

                // Insert a table cell:
                var cellName = row.insertCell(0);
                // Create an input field for the name:
                var elName = document.createElement('input');
                elName.type = 'text';
                elName.size = 10;
                elName.id = 'txtProductName' + globalControlCounter;

                // Add the span that will represent the validotor
                // (in this case the required field validator):
                var elNameValidator = document.createElement('span');
                elNameValidator.style.color = "Red";
                elNameValidator.style.display = "none";
                elNameValidator.id = elName.id + "Validator";
                elNameValidator.controltovalidate = elName.id;
                elNameValidator.errormessage = "<b>Field is incorrect</b>
                                     <br /> <span>Name is a required field.</span>";
                elNameValidator.validationGroup = "EditItems";
                elNameValidator.initialvalue = "";
                elNameValidator.evaluationfunction =


The next step is to add the validator to the array of existing validators:


                // Push the new validator inside the page validators array:


After this is done, we can add the validator callout extender control, that will add some nice pop out effects displaying the error message itself:


                // Now lets bind the validator callout that will popup
                // up when the field is not valid:
                $create(AjaxControlToolkit.ValidatorCalloutBehavior, {
                    "closeImageUrl": "/image/close.png",
                    "highlightCssClass": "highlight",
                    "id": elNameValidator.id + "ValidatorCalloutExtender",
                    "warningIconImageUrl": "../images/attention.png"
                }, null, null, $get(elNameValidator.id));


The last step that needs to be taken and is essential for this to work is to add some dummy validator and dummy validator callout extender to the page. This is needed, as otherwise the necessary javascript libraries will not be included on the page (either this, or including the libraries by hand, whichever solution you prefer).


Now, the triggering of the validators is up to you – I used triggering when the user clicks some submit action. Since the action does not cause a postback, I needed some client side validation check. If you have the same problem, you can check out this simple solution located on this post.


As you can see, it is really easy to create the validation and add the validator callout extenders, with just a bit of knowledge in javascript. I recommend experimenting with different types of validators, as they all attach different attributes to the DOM element. If you have any questions or suggestions, feel free to post them to the comments section, I will try my best to help.

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ASP.NET AJAX 4.0 Templates Simple Demo - Step by Step

by Sergio 27. November 2009 02:59

This quick step by step tutorial is made with Visual Studio 2010 beta2
and ASP.NET AJAX 4.0 Preview 6.
It is possible that some properties and/or methods will be changed in future versions, but so far this is the way to use client side templates in ASP.NET AJAX 4.0.



First you should download appropriate software:

  1. Microsoft .NET Framework 4.0
  2. Microsoft Visual Studio 2010
  3. ASP.NET Ajax Library


For your first project you should use web site or web project visual studio templates, create new project and add appropriate scripts to a project.

For this example I’ve created a new web site and added all the AJAX scripts we need to a folder named “MicrosoftAJAX” (look at the picture).




Also I have created a simple demo xml web service to be used from client side to read data for our template.


   1:  <%@ WebService Language="C#" Class="DemoService" %>
   3:  using System;
   4:  using System.Web;
   5:  using System.Web.Services;
   6:  using System.Web.Services.Protocols;
   8:  [WebService(Namespace = "http://icodefactory.com/", 
   9:     Description="Demo web service used by client side templates")]
  10:  [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
  11:  // To allow this Web Service to be called from script, 
  12:  // using ASP.NET AJAX, uncomment the following line. 
  13:  [System.Web.Script.Services.ScriptService]
  14:  public class DemoService  : System.Web.Services.WebService {
  16:      [WebMethod(Description="Returns Demo Contacts data")]
  17:      public Contact[] GetContacts() {
  18:          Contact[] contacts = new Contact[3] {
  19:              new Contact(){ Id=1, Name = "John", Lastname="Doe" },
  20:              new Contact(){ Id=2, Name = "Joan", Lastname="Smith" },
  21:              new Contact(){ Id=3, Name = "Brad", Lastname="Forbs" }
  22:          };
  23:          return contacts;
  24:      }
  26:  }


Pay attention that you have to set the ScriptService attribute so your web service can be used from JavaScript.


Finally we have to add some simple html (yes, pure html) file and import appropriate scripts:

  • MicrosoftAjax.js
  • MicrosoftAjaxTemplates.js

for AJAX client side libraries and

  • DemoService.asmx/jsdebug

for access to the xml web service.


   1:  <script src="MicrosoftAJAX/MicrosoftAjax.debug.js" 
   2:          type="text/javascript"></script>
   3:  <script src="MicrosoftAJAX/MicrosoftAjaxTemplates.debug.js"
   4:          type="text/javascript"></script>
   6:  <script src="DemoService.asmx/jsdebug" 
   7:          type="text/javascript"></script>


We also need some styling on the page. Class ‘sys-template’ is used to hide empty table before data is bound from the service by using AJAX DataView client side control.


   1:  <style type="text/css">
   2:          /*Used to hide empty table*/
   3:          .sys-template
   4:          {
   5:              display: none;
   6:          }
   7:          /* Style of table that shows data*/
   8:          .table_style
   9:          {
  10:              background-color: Olive;
  11:              padding: 5px 5px 5px 5px;
  12:          }
  13:      </style>


Now, time for JavaScript that should load the data from the xml web service, fill the DataView object and bind the data to the html template.


<script type="text/javascript">
        // ASP.NET Ajax client side control - DataView
        var contactsView;
        // Triggers on page load
        function pageLoad() {
            // Create Contacts DataView
            contactsView = 
                      $create(Sys.UI.DataView, {}, {}, {}, $get("contactsBody"));

            // Load Contacts from web service
        function ContactsLoaded(contactsData) {
            // Display data in Contacts DataView


The pageLoad function creates the DataView client side object and calls the xml web service to populate the object with data.

On successful service call the data is bound to the html with a simple call to the set_data() function.


This is how your template should look:


   1:  <table class="table_style" border="0" cellpadding="4" cellspacing="4">
   2:          <thead>
   3:              <tr>
   4:                  <th>
   5:                      Name
   6:                  </th>
   7:                  <th>
   8:                      Lastname
   9:                  </th>
  10:              </tr>
  11:          </thead>
  12:          <!-- tbody tag id is used to identify tag in DOM that are going to be
  13:               used by the DataView. Class is set to 'sys-template' in order to
  14:               hide empty table -->
  15:          <tbody id="contactsBody" class="sys-template">
  16:              <tr>
  17:                  <td>
  18:                      {{ Name }}
  19:                  </td>
  20:                  <td>
  21:                      {{ Lastname }}
  22:                  </td>
  23:              </tr>
  24:          </tbody>
  25:      </table>


<tbody> tag is used to become a template for the data in the DataView object.

DataView will change HTML with appropriate tags and generate table rows for every data row from the xml web service method call.

{{ Name }} and {{ Lastname }} parts will be replaced with actual data.


At the end you have your data.




Hope this will help you start with the new templates. Web development is moving to client side and everyone should embrace the client side because of its many benefits, like responsiveness, bandwidth and UI patterns.


Demo Solution may be downloaded from our public download section.

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