Friday, May 7, 2010

How to set programmatically a value of a watermarked TextBox via JavaScript - Update

Some time ago I've published an article How to set programmatically a value of a watermarked TextBox via JavaScript about some specifics of working with a text input box decorated with a TextboxWatermark Ajax Extender control from the Ajax Control Toolkit library. The technique described in the article has proven useful for a number of developers so when the new release of the Ajax Control Toolkit has recently been announced I've decided to update the article to cover some of the braking changes in Ajax Control Toolkit components.

Ajax Control Toolkit changes

One of the most significant changes in the recent Ajax Control Toolkit release that affected everything is renaming namespaces and control names. Most of the JavaScript classes in the ACT has been moved into Sys.Extended.UI and some of them renamed.

Correspondingly the AjaxControlToolkitTextboxWrapper class that is crucial for the technique described in this article is now called Sys.Extended.UI.TextBoxWrapper and this is a breaking change. Most if its methods haven't been renamed and this is a good news however the new way of using the wrapper has been introduced.

Below are the code examples demonstrating how to write the code correctly with the new version of the ACT.

First we need to acquire an instance of the Sys.Extended.UI.TextBoxWrapper class for our textbox control and this is the newly introduced technique compared to the previous version of the ACT:
// get the instance of a textbox element
var textBox = $get(textBoxId);
// use the get_Wrapper static method of the TextBoxWrapper class to get the instance of the wrapper for the textbox
var wrapper = Sys.Extended.UI.TextBoxWrapper.get_Wrapper(textBox);

In the code above first I assume that the ACT is present so I don't have to check that Sys.Extended.UI namespace is defined. Secondly the code above is safe even if the textbox is not watermarked: the get_Wrapper static method will always return the instance of the TextBoxWrapper; the new instance will be created if the textbox is not watermarked.

Now we can set or get a value of the textbox using the instance of the TextBoxWrapper:
// get the textbox value
var oldValue = wrapper.get_Value();
// set the textbox value


In a nutshell there are two major changes introduced in the new ACT release that affect the coding technique described here: the name of the textbox wrapper class has been changed; and now it's not required to check whether the textbox is watermarked to use the technique above.


  1. I tried this for a textbox with a watermark extender, but I get error:
    Message: 'Sys.Extended.UI' is null or not an object

  2. Asmund, this method only works for the latest version of the Ajax Control Toolkit. If you are using one of the older versions of ACT read the previous version of the article:

  3. I can change the text but the watermark effect is gone.

  4. Is anybody got success or know alternative method to achieve this? My requirement is to get SSN and onblur just show last four digits.