jquery code is not workign after postback

I wrote the following jquery code to allow only numbers in a textbox.

$("[id$='txtPriority']").keydown(function (event) {
                if (event.keyCode == 48) {
                    var value = $("[id$='txtPriority']").val();
                    if (value == "") {
                      开发者_StackOverflow  event.preventDefault();
                        return;
                    }
                }
                else if (event.keyCode == 86 || event.keyCode == 118) {
                    event.preventDefault();
                    return;
                }
                else {
                    $("[id$='txtPriority']").numeric();
                }
});
});

This works fine ,when the page is loaded for first time.But after post back the code is not working.What might be the reason.

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I you are changing something with ajax then the event will not work. Try using the live function ( http://api.jquery.com/live/ )

$("[id$='txtPriority']").live('keydown', function (event) {

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I had this problem once and it was because I was replacing the html for the form in the postback. You need to reset your event handlers after replacing the controls or use the .live() handler which will work even for elements you add later:

$("[id$='txtPriority']").live('keydown', function (event ) {