I have a modal dialog in which I have a text field I want to pass a value to controller.
Pop-up dialog is as follows
@using (Html.BeginForm("Index", "QC", FormMethod.Post, new { id = "qcForm" }))
{
...
    <div id="dialog-form" title="Add Feedback">
        <p class="validateTips">Please enter Feedback :</p>
        @Html.TextBoxFor(m => m.RejectionReason, new { @class = "required" })
    </div>
...
}
Submits as follows
$(document).ready(function () {
    $('#btnRejectAll').click(function(event) {
        event.preventDefault();
        $("#dialog-form").dialog("open");
    });
    $("#dialog-form").dialog({
        autoOpen: false,
        height: 300,
        width: 420,
        modal: true,
        resizable: false,
        buttons: {
            "Submit": function () {
                $("#qcForm").submit();
            },
            Cancel: function () {
                $(this).dialog("close");
            }
        },
        close: function () {
            $(this).dialog("close");
        }
    });
});
If I have the textbox just in my form and not in dialog it submits fine. But in the dialog it comes in as NULL in the controller.
 
    