Validation <input type="file"> with JQuery Validation Plugin
<p>I use <a href="http://docs.jquery.com/Plugins/Validation" rel="nofollow">JQuery Validation Plugin</a> to validate my form and it works for all fields,<br>
but when I try to use it for  <code>&lt;input type="file" id="ProjectInformation"&gt;</code>  </p>

<pre><code>&lt;script&gt;
    $(function() {
        $("#feedback-form").validate({
            submitHandler: function(form) {
                form.submit();
            },
            rules: {
                Name: {
                    required: true,
                    minlength: 2
                },
                ProjectInformation: {
                    extension: "doc,txt,pdf",
                }
            },
            messages: {
                Name: {
                    required: "Please enter a name",
                    minlength: "Name must consist of at least 2 characters"
                },
                ProjectInformation: {
                    extension: "Only .doc, .txt, and .pdf files allowed",
                }
            }
        });
    });
&lt;/script&gt;
</code></pre>

<p>I get error <strong>Uncaught TypeError: Cannot call method 'call' of undefined</strong><br>
What's wrong? </p>
