jQuery Ajax validation and DataAnnotations attributes

I created a form that posts and gets results through jQuery AJAX. Now I need to put some validation stuff on it. I wonder how to do it. Should I use jQuery validation plugin? If I use it and if I'm guessing right - there is no need to decorate the model with DataAnnotations attributes, they no longer gonna make any sense, right?

So basically that I'm saying: I use a normal html form Html.BeginForm(), not an AJAX form, then I override the form's submit() function

$("form[action$='UpdateCalendarForm']").submit(function () 
{
    $.ajax({
            url:  $(this).attr("action"),
            contentType: 'application/json; charset=utf-8',
            type: "POST",
            data: JSON.stringify(calendarData),
            dataType: "json", 
            success: updateCalenda开发者_JAVA技巧rCallback
           });
    return false; // it wouldn't actually rerender the page
});

function updateCalendarCallback(result){
 // And here I just do something on the page
}

What's the best way to add some validation here without Ajax helper methods (but using jQuery) and DataAnnotations attributes on the Model properties.

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Brad Wilson had great video on mvcConf about validation. Here's everything you will need to know to start implementing custom validation on mvc3