Jquery function does not display variable value

var subTot = 0;
$('#Discount').val(0);
var PID = 0;
var ProductName;

$(function () {
    $('select#DProducts').change(function () {
        ProductName = $("[id*='DProducts'] :selected").text();
      ////  alert(ProductName);
      //  $.getJSON("/Sale/SelectedItemId/" + $("#DProducts > option: selected").attr("value"), function (data) {
      //      PID = data.Val();
      //  });
    });
});


$(document).ready(function () {


    var orderItems = [];
    //Add button click function
    $('#add').click(function () {
        //Check validation of order item
        var isValidItem = true;
        if ($('#DProducts').val() == '') {
            isValidItem = false;
            $('#DProducts').siblings('span.error').css('visibility', 'visible');
        }
        else {
            $('#DProducts').siblings('span.error').css('visibility', 'hidden');
        }

        if (!($('#quantity').val() != '' && !isNaN($('#quantity').val()))) {
            isValidItem = false;
            $('#quantity').siblings('span.error').css('visibility', 'visible');
        }
        else {
            $('#quantity').siblings('span.error').css('visibility', 'hidden');
        }

        if (!($('#UnitPrice').val()!= '' && !isNaN($('#UnitPrice').val()))) {
            isValidItem = false;
            $('#UnitPrice').siblings('span.error').css('visibility', 'visible');
        }
        else {
            $('#UnitPrice').siblings('span.error').css('visibility', 'hidden');
        }

        //get ProductId


        //Add item to list if valid
        if (isValidItem) {
            orderItems.push({
                ProductId: PID,
                Quantity: parseInt($('#quantity').val()),
                UnitPrice: parseFloat($('#UnitPrice').val()),
                SubTotal: parseInt($('#quantity').val()) * parseFloat($('#UnitPrice').val())
            });


            subTot = subTot + (parseInt($('#quantity').val()) * parseFloat($('#UnitPrice').val()))


            //Clear fields
          //  $('#DProducts').val('').focus();
            $('#quantity,#UnitPrice').val('');


        }
        //populate order items
        GeneratedItemsTable();

        $('#SubTotal').val(parseFloat(subTot));
        $('#NetTotal').val(parseFloat(subTot) - parseFloat($('#Discount').val()));


    });
    //Save button click function
    $('#submit').click(function () {
        //validation of order
        var isAllValid = true;
        if (orderItems.length == 0) {
            $('#orderItems').html('<span style="color:red;">Please add order items</span>');
            isAllValid = false;
        }

        if ($('#AccountInvNo').val().trim() == '') {
            $('#AccountInvNo').siblings('span.error').css('visibility', 'visible');
            isAllValid = false;
        }
        else {
            $('#AccountInvNo').siblings('span.error').css('visibility', 'hidden');
        }

        if ($('#SaleDate').val().trim() == '') {
            $('#SaleDate').siblings('span.error').css('visibility', 'visible');
            isAllValid = false;
        }
        else {
            $('#SaleDate').siblings('span.error').css('visibility', 'hidden');
        }

        if ($('#Customer').val().trim() == '') {
            $('#Customer').siblings('span.error').css('visibility', 'visible');
            isAllValid = false;
        }
        else {
            $('#Customer').siblings('span.error').css('visibility', 'hidden');
        }

        //Save if valid
        if (isAllValid) {
            var data = {
                AccntInvoiceNo: $('#AccountInvNo').val(),
                SaleDate: $('#SaleDate').val(),
                SubTotal: $('#SubTotal').val(),
                Discount: $('#Discount').val(),
                NetAmount: $('#NetTotal').val(),
                SaleType: 1,
                CustomerId: 2,
                UserId: 1,
                SaleDescs: orderItems
            }

            $(this).val('Please wait...');

            $.ajax({
                url: '/Sale/SaveOrder',
                type: "POST",
                data: JSON.stringify(data),
                dataType: "JSON",
                contentType: "application/json",
                success: function (d) {
                    //check is successfully save to database
                    if (d.status == true) {
                        //will send status from server side
                        alert('Successfully done.');
                        //clear form
                        orderItems = [];
                        $('#AccountInvNo').val('');
                        $('#saleDate').val('');
                        $('#orderItems').empty();
                        $('#SubTotal').val('');
                        $('#Discount').val('');
                        $('#NetTotal').val('');
                    }
                    else {
                        alert('Failed');
                    }
                    $('#submit').val('Save');
                },
                error: function (exception) {
                    alert('Exeption:' + exception);
                    $('#submit').val('Save');
                }
            });
        }

    });
    //function for show added items in table
    function GeneratedItemsTable() {



        if (orderItems.length > 0) {
            var $table = $('<table/>');
            $table.append('<thead><tr><th>Item</th><th>Quantity</th><th>Unit Price</th><th>Total</th></tr></thead>');
            var $tbody = $('<tbody/>');
            $.each(orderItems, function (i, val) {
                var $ProductName2 = $("[id*='DProducts'] :selected").text();
                var $row = $('<tr/>');
                $row.append($('<td/>').html(val.ProductName2));
                $row.append($('<td/>').html(val.Quantity));
                $row.append($('<td/>').html(val.UnitPrice));
                $row.append($('<td/>').html(val.SubTotal));
                var $remove = $('<a href="#">Remove</a>');
                $remove.click(function (e) {
                    e.preventDefault();
                    orderItems.splice(i, 1);
                    GeneratedItemsTable();
                });
                $row.append($('<td/>').html($remove));
                $tbody.append($row);
            });
            $table.append($tbody);
            $('#orderItems').html($table);
        }
        else {
            $('#orderItems').html('');
        }
    }


});