//創建(jian)訂單使用knockoutJs
    var CreateOrder = function () {
        var self = this;
        self.productid = ko.observable().extend({
            required: true
        });
        self.productname = ko.observable().extend({
            required: true
        });
        self.username = ko.observable().extend({
            required: true
        });
        self.price = ko.observable().extend({
            required: true,
            min: { params: 1, message: "價格要是大于(0)的整數！" }
        });
        self.count = ko.observable().extend({
            required: true,
            min: { params: 1, message: "您最少也要買一個吧！" },
            max: { params: 100, message: "最大一次只能買(100)個！" }
        });
        self.Do = function () {//ko方法(fa)名需要(yao)是大寫的
            self.errors = ko.validation.group(self);
            if (self.isValid()) {
                $.ajax({
                    url: "/order/doOrder",
                    type: "POST",
                    data: { productid: self.productid(), productname: self.productname(), price: self.price(), count: self.count(), username: self.username() },
                    success: function (data) {
                        if (data.code == 1) {
                            location.href = location.href;
                        }
                        else
                            alert(data.code);
                    }
                })

            } else {
                self.errors.showAllMessages();
            }
        }
    }
    ko.applyBindings(new CreateOrder());

        public JsonResult DoOrder(int productid, string username, string productname, decimal price, int count)
        {

            var entity = new Entity.Order_Info
            {
                TotalPrice = price * count,
                UserId = userid,
                UserName = username,
                AddDate = DateTime.Now,
                Info = "用戶下單",
                Order_Detail = new List<Order_Detail> { new Order_Detail { Count = count, ProductId = productid, ProductName = productname, SalePrice = price } }
            };

            if (productid <= 0)
            {
                ModelState.AddModelError("ProductId", "商(shang)品(pin)ID不合法...");
            }

            #region 在action里拼接ModelState錯誤消息
            var errors = new StringBuilder();
            foreach (string key in ViewData.ModelState.Keys)
            {
                ModelState modelState = ViewData.ModelState[key];
                foreach (ModelError error in modelState.Errors)
                {
                    errors.Append(error.ErrorMessage + ",");
                }

            }
            #endregion

            if (entity.IsValid && ModelState.IsValid)
                orderService.DoOrder(entity);
            else
                return Json(new { code = entity.GetRuleViolationMessages() + errors });

            return Json(new { code = 1 });
        }