You should check what the name of that form field really is. If you're using Web Forms and the control is in a container, it'll by something like Ctl1_txtMyTextBox or something along those lines.

Use your DevTools of choice and Inspect Element to find out what hte real ID is then use that name instead.

$("#Ctl1_txtMyTextBox").change(...);

FWIW, in the past I've used a function that helps me with this:

$$ = function (id, context) {
        /// <summary>
        /// Searches for an ID based on ASP.NET naming container syntax.
        /// First search by ID as is, then uses attribute based lookup.
        /// Works only on single elements - not list items in enumerated
        /// containers.
        /// </summary>    
        /// <param name="id" type="var">Element ID to look up</param>    
        /// <param name="context" type="var">
        /// </param>    
        /// <returns type="" /> 
        var el = $("#" + id, context);
        if (el.length < 1)
            el = $("[id$=_" + id + "],[id*=" + id + "_]", context);
        return el;
    };

You can then use it like this:

$$("txtMyTextBox").change(function() { alert('exit') });

and it'll find anything that matches this name regardless of the WebForms container prefixes.

+++ Rick ---

>I am trying to incorporate a jQuery Change function in an asp.net page that would make certain control invisible when user starts typing (making changes) in a text box. My initial test, just to call an alert() does not seem to work. Here is my code:
>
>

><script type="text/javascript">
>       $(document).ready(function () {
>
>           $("txtMyTextbox").change(function () {
>
>               alert("Change Function Called");
>
>           });
>
>   })
></script>
>

>
>What is wrong with my code? TIA