Wednesday, April 15, 2009

Hide/Show validator callout control using javascript

In my previous blog we saw how to call validation controls from javascripts. This blog we will see how to show and hide a ASP.NET AJAX’ (AJAXControlToolkit) ValidatorCalloutExtender control using javascript. Below is an aspx page with a validator callout control.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="AJAXControls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">
<html xmlns="">
<head runat="server">
    <title>Untitled Page</title>

    <form id="form1" runat="server">
        <!--ASP.NET Drop down control-->
        <asp:DropDownList ID="status" runat="server" >
            <asp:ListItem Selected="True" Text="Select" Value="0" />
            <asp:ListItem Text="One" />
            <asp:ListItem Text="Two" />
            <asp:ListItem Text="Three" />
        <!--ASP.NET Required Field Validator to validate the drop down.-->
        <asp:RequiredFieldValidator ID="statusValidator" runat="server" ErrorMessage="Please choose a value other than 'Select'"
            ControlToValidate="status" InitialValue="0" Visible="true">
    <!--Validator callout control-->
        <AJAXControls:ValidatorCalloutExtender ID="statusValidator_ValidatorCalloutExtender"
            runat="server" TargetControlID="statusValidator">
        <asp:Button ID="submit" Text="Submit" OnClientClick="javascript:return ValidatePage();"
            runat="server" />
    <asp:ScriptManager ID="ScriptManager1" runat="server">

The above code has a dropdown control with an ASP.NET required field validator control and a validator callout control attached to it. As soon as you click the submit button and if there is a validation error the error will be popped out in the validator callout control as shown below.

Error in Validator callout control

Popping of the error message in a validator callout control happens automatically. But there may be scenario where you would like to hide or show the validator control using javascript. The below sample code does exactly that.

<script language="javascript" type="text/javascript">
function ValidatePage()
    //Function which calls the whole validation for the page.
    if (Page_ClientValidate())       
        return true;
        return false;
//User defined method which hides the AjaxControlToolkit ValidatorCalloutExtender control
function hideValidatorCallout()
    //Below code hides the active AjaxControlToolkit ValidatorCalloutExtender control.
    setTimeout(showValidatorCallout, 3000);   

function showValidatorCallout()
    //Gets the AjaxControlToolkit ValidatorCalloutExtender control using the $find method.
    AjaxControlToolkit.ValidatorCalloutBehavior._currentCallout = $find('<% =statusValidator_ValidatorCalloutExtender.ClientID %>');
    //Below code unhides the AjaxControlToolkit ValidatorCalloutExtender control.;

From the above code we can see that there is a code something like this “AjaxControlToolkit.ValidatorCalloutBehavior._currentCallout”. The _currentCallout property will hold the current validator callout control. Whenever there is a validation failure and if there is validator callout control associated with validator control, the _currentCallout property will be assigned the validator callout control. To hide the validator callout control you need to use the “hide”  javascript function along with the _currentCallout property as shown below.


At any given point the _currentCallout property will have only one validator callout assigned, this is to avoid the confusion or dirtiness which can arise by showing all the validator callout control. If all the validator callouts are shown when multiple validation fails then the screen will be cluttered with all the validator callouts popping here and there. To avoid this cluttered view this approach of showing only one validator callout control has been taken.

Similarly to show the validator callout control you can use the “show” javascript method along with _currentCallout property as shown below.

//Gets the AjaxControlToolkit ValidatorCalloutExtender control using the $find method.
    AjaxControlToolkit.ValidatorCalloutBehavior._currentCallout = $find('<% =statusValidator_ValidatorCalloutExtender.ClientID %>');
    //Below code unhides the AjaxControlToolkit ValidatorCalloutExtender control.;

But the above code if used just like that can throw the following error.

Microsoft JScript runtime error: 'this._popupBehavior' is null or not an object

The reason why this happens is that we have not called either ValidatorEnable or ValidatorValidate javascript functions. These two functions set the necessary things, like _popupBehavior property, for the validator control to work properly. Validator callout controls are not meant to be shown directly they are actually extender controls which extend the functionality of the validation control and these controls are shown automatically when a validator control’ validation condition fails. So if you want to show a validator callout function just call ValidatorEnable or ValidatorValidate javascript function.

That’ about it, on how to hide and show validator callout controls using javascript. I know I have not mentioned anything about “$find” javascript function. We will have a discussion on this in my subsequent blog. For the time being just understand it as a shortcut method to find a component. In our next blog we will see how to set focus to a particular tab in the AjaxControlToolkit’ tab container control.

Some important methods of ValidatorCallout controls

Methods/Properties Description
_getErrorMessage() Gets/returns the error message
get_closeImageUrl() Gets/returns the close image url at the top rightmost corner of the validator callout control. Default is an x mark.
get_isOpen() Gets/returns a boolean value indicating whether the validator callout is opened or not.
get_warningIconImageUrl() Gets/returns the warning icon image’ url. Default is an exclamation mark inside a triangle.
get_width() Gets/returns the width of the validator callout control.
hide() Function to hide the validator callout control.
set_closeImageUrl(imageUrl) Function to set the close image url. One can use this method to change the default X mark.
set_warningIconImageUrl(imageUrl) Function to set the warning image. One can use this function to change the default exclamation image used for warning.
set_width(int) Function used to set the width of the validator callout control.
show() To show the validator callout control.
_closeImageUrl Property to get/set the close image.
_warningIconImageUrl Property to get/set the warning image.
_width Property to get/set the width of the validator callout control
_popupBehavior Property using which one can work with the pop up behaviour of the validator callout control.
_errorMessageCell Property using which one can modify the error message.

Some methods of ValidatorCallout._popupBehavior property

Below are listed few of the _methods of _popupBehavior property of validator callout function. These methods are available with only _popupBehavior property. If one wants use these methods then one has retrieve the _popupBehavior property from  validator callout control by any of the following two means shown below.

//Retrieving the validator callout control using the $find helper method.
var valCallout = $find('<%=statusValidator_ValidatorCalloutExtender.ClientID %>');
//Get the _popupBehavior property in a variant object and then
//use the required methods.
var popUpBehavior = valCallout._popupBehavior;
//Directly use the methods along with the _popupBehavior property as shown below.

After retrieving the _popupBehavior property by any of the above means you can use the following methods.

Methods/Properties Description
get_x() Method to get the X coordinates of the validator callout control
get_y() Method to get the Y coordinates of the validator callout control.
get_visible() Methods that returns a boolean value specifying whether the validator callout control is visible or not.
set_x(x_coordinate) Method to set the X coordinate for the validator callout control. Method takes an integer value as an argument.
set_y(y_coordinate) Method to set the Y coordinate for the validator callout control. Method takes an integer value as an argument.

Some methods of ValidatorCallout._errorMessageCell property

Since _errorMessageCell returns a TD (cell) object there is nothing much new it has all the methods/properties corresponding to a cell object. One use of this property is to change the error message of the validator callout extendor control using javascript. To change the error message using javascript see the code below.

//Retrieving the validator callout control using the $find helper method.
var valCallout = $find('<%=statusValidator_ValidatorCalloutExtender.ClientID %>');
//Get the error message cell.
var messageCell = valCallout._errorMessageCell;
//Changing the error message.
messageCell.innerHTML = "Changed:)";

Mail from my blog reader

Recently one of my blog reader mailed me across some problems he was facing with validator callout control. For the benefit of the readers I am pasting the mail chain discussion here, with prior permission from the reader who mailed me.

Hey Sandeep, how are you?

I've read your amazing article on:

thank you very much, it really help me!

So, I want to call all validators, and them call the specific callout,
since we can access  Page_Validators[validatorIndex]...

I could execute all the validators, but now I need to know the name of
validator to call the callout.

var validator = Page_Validators[validatorIndex];

do you know how to get the id of the validator?

validator.Id ? validator.ClientId ?

thank you !

this is my solution for now:

<script language="javascript" type="text/javascript">
    var Page_Callout = new Array("<%
=statusValidator_ValidatorCalloutExtender.ClientID %>");

    function ValidatePage() {

        if (typeof (Page_Validators) == "undefined") return;

        var noOfValidators = Page_Validators.length;

        for (var validatorIndex = 0; validatorIndex < noOfValidators;
            var validator = Page_Validators[validatorIndex];


            if (!validator.isvalid) {

                var tabPanel = validator.parentElement.control;
                var tabContainer = tabPanel.get_owner();


                return false;
            return true;

    function hideValidatorCallout() {

    function showValidatorCallout(currrentCallout) {
_currentCallout =currrentCallout;

-- My reply--

If I am not wrong when you are calling the function "showValidatorCallout" it doesn't show the validator callout in the tab? Am I right? If yes I have also faced the same problem. I solved this by a dirty hack. So what I did is something like this.

ValidatorEnable(dropDownValidator); //Calling the validator callout for the first time. Just a dummy call.
if (!dropDownValidator.isvalid)
     setActiveTabIndex(0); //Method which sets the active index.
     hideCurrCallout(); //Method which hide the current validator callout
     ValidatorEnable(dropDownValidator); //Calling ValidatorEnable method for the second time.

Hope this helps. So when you work with tab you have to use the above hack to display validator callout control. I didn't get much time to find out the reason behind but will try find out.

--Response from the reader--
Hey Sandeep, thanks...

I've another problem with the callout's... Please, take a loot in that
image attached.. do you have this problem ?
When the field is in the right side... the callout create scrolls and
expand the width of the page :(

Do you know how to avoid this ?

--My reply--
Hope your previous problem has been solved. This is the auto behaviour of the browser where if something is dynamically created and it exceeds the width of the browser it will give you a scroll bar. For this you can set the X and Y coordinates of the callout control so that they won't exceed the width of the browser. To set the X and Y coordinates you can use the following code.

//Retrieving the validator callout control using the $find shortcut method.
var valCallout = $find('<%=statusValidator_ValidatorCalloutExtender.ClientID %>');
//Setting the X coordinates
//Setting the X coordinates

or you can use the below code.


Hope this solves your problem.

--Reader response--
Hi Sandeep,

Yeah... you solve the problems :)

thank you again.



  1. hi m not en expert like u people out there..nd dont knw whr to ask a question so m simple sharing my prob.with u... if m wrong somewhre pls correct me buddy.. pls guide me out in solving this problem...
    I have a webform with a checkboxlist with about 20 items.. and i have used a javascript snippet to validate that at least one item is selected out of the checkboxlist.. till now this works fine... but becoz of using this javascript snippet on the submit button's ONCLIENTCLICK event, all of my validators on the page and all the validatorcalloutextenders have stopped working i.e now they are not popping up and the page simply postbacks. and when i remove this javascipt snippet from the OnClientClick, then all those validators and validatorcalloutextenders works just fine....
    Hope u understand my prob... Pls give me some suggestion will be highly appriciated...

  2. Hi Anonymous,
    So your problem is that your writing custom validation to validate some control in the UI and after that you want the validation controls in the page to fire. Just call Page_ClientValidate() javascript function after your custom javascript logic. Page_ClientValidate() is an ASP.NET runtime generated javascript function which will call/trigger all the validation controls. I hope this helps you. If not do let me know. Also if the validation are not sucessfull and you don't want to postback the page then just return false from the javascript function. Returning a false value will not trigger postback. You can go through my blog "" and know about various javascript functions to call validator controls.


  3. Hello, great write-up with good info about the Validator extender, I wish I found this a long time ago. I am having a problem with updating the error message in an extender. I am using the .errormessage property, and have tried the innerHTML as your blog mentioned, but neither actually update the error message after the first time. I created a post about my issue here:

    Any ideas on that one?

  4. Hi,
    What do you mean by "First time"? Could you shed more light on that? Also I have seen you code in the pasted link. Is the sender object a validation control?

  5. Hello, by first time I mean if you enter an incorrect value, the callout will display the correct error message with the correct range (the lowRange and highRange). After that, if you enter a new invalid value that has a different lowRange and highRange, the callout will not display the new range, but will still display the range from the first validation message. If I display the regular validator message (not the callout), the correct values will be displayed every time. So it is just that the ValidatorCalloutExtender will not get its error message updated. And yes, the sender is the CustomValidator. Thanks!

  6. Hi,

    I have an issue where the callout validator control shows through in IE when placed next to a drop downlist..meaning the error message is not fully visible since the control is transparent and the control below it are visible. Do you have suggestion to solve this issue?


  7. Hi DP,
    Could you send me an email with an image attached showing your problem. My email id is

  8. This comment has been removed by the author.

  9. I found this hack for re-setting the text of a callout and it's worked pretty well for me in my Custom Validators.

    var cell = sender.ValidatorCalloutBehavior._errorMessageCell;
    //Cell is going to be null first time
    if (cell != null) {
    cell.innerHTML = sender.errormessage;

  10. Thanks Michael, for sharing the info.

  11. Hello Sandeep,
    Nice article!!I have a doubt pls can you help me to solve my pblm. I want to expand the link say syllabus and show its content or data under it which is in the database.
    like +Syllabus
    when i expand this ,i want its data to be shown under it
    This is a concept.........
    Hope you got my problem..Could you pls help me out frm this pblm.Kindly waiting for ur reply.
    Myself Neha

  12. Hi Neha,
    For your problem there are two possible solution. If you want to show the content on the click of the plus symbol or image, you can use ASP.NET AJAX' "CollapsiblePanel" control.
    If you want to show multiple content in different accordians then you can use the "Accordian" control in the ASP.NET AJAX toolkit.

  13. Thank you very much for your reply Sandeep. My alias name is Neha.. I will use the ajax control and try to solve the issue. Once again thank u.

  14. Hello Sandeep.How to load the data which is in the database table. Syllabus data is in the BookTable thru the column i need to retreive.The control which u told,can v retreive the database content? Please help me.Kindly request.

    Thank you in advance

  15. Hi Neha,
    I doubt whether it is a databound control. Even if it is not you can very well write code to retrieve data from the database and pump the same to the controls content elements. I would suggest to take a look at the control and understand it and then customise it to your requirement.

  16. Hi Sandeep. Do you have a solution on reassigning the TargetControlID of a callout extender? I'm encountering this issue whereby I can clone the bottom row of a table dynamically, and there's no limit on the number of rows that can be added (cloned.) The row itself contains several controls including a textbox with custom validator & callout extender. Since it is a clone, the IDs are the same and won't work, and in fact raises an exception when I call Page_ClientValidate. A help/guide would be much appreciated.

  17. Can you please give me idea to show all the callout extender at the same time of button click. i.e when we submit the form I need to display all the callout extender opened view. Please help me on this.

  18. If I am not wrong it is not possible to display all the callout at the same time. For this you will have to use validation summary control.

  19. Thanks!!It worked for me...

  20. Do you know how to find out which validatorCallOut is exactly open?

  21. Hi,
    If I am not wrong the "_currentCallout" property will hold the active validator call out.

  22. Hi Sandeep ,

    thanks for the code.

    It works like a charm.

    ram sagar mourya

  23. hi sir this is kusuma now we are doing mini project, i have doubt on how to do validation for login form by using javascript with out using validation controls in,normally form consists of username and password,user name must be 6 characters and username should not be the special characters,and password also same.sir plz sir can u send me the code,its very urgent Email id is,

    1. Hi Kusuma,
      You can do the validation using Javascript. The validation is pretty easy and I think with little bit of effort you easily do it yourself. there are lot of e.g. in the net. Just google around and you will be good to go.

  24. hiiiii sir...
    can u plz tell me how to use print dialog control in

  25. Hi Sandeep,
    I tried the above code but its saying me that AjaxControlToolkit is undefined r null i have referenced also the AJAXCONTROLTOOLKIT. Can u pls reply me asap. Thanks

  26. Hi all,
    I tried some of code listed above but AjaxControlToolkit is undefined error appears even if i reference ajaxtoolkit set CombineScript to true.


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