Adding coupon code fields to MVC checkout processes

The Kentico E-commerce Solution can process coupon codes for several types of discounts and offers:

Customers who obtained a coupon code are eligible to receive a discount or redeem a gift card (based on the configuration of the discount or gift card).

When building a checkout process on an MVC site, you may want to add an input text box that allows customers to enter coupon codes. The system validates whether a specified coupon code provides a discount. In Kentico MVC projects, the Kentico.Ecommerceintegration package provides an API for working with coupon codes.

To add a coupon code input to your MVC site:

Open your MVC project in Visual Studio.
Edit the controller class that you use for your checkout process (see Using a shopping cart on MVC sites).

Implement two POST actions – one for adding coupon codes to the current shopping card and another for removing coupon codes.

To add and validate coupon codes, call the AddCouponCode method of the ShoppingCart object representing the current shopping cart.

The AddCouponCode method returns a true value if the specified coupon code provides a valid discount for the current shopping cart and customer.

To remove coupon codes, call the RemoveCouponCode method of the ShoppingCart object.




          /// <summary>
          /// Adds the specified coupon code to the shopping cart.
          /// </summary>        
          [HttpPost]
          public ActionResult AddCouponCode(string couponCode)
          {
              // Gets the current user's shopping cart
              ShoppingCart currentCart = shoppingService.GetCurrentShoppingCart();

              // Adds the coupon code to the shopping cart
              // The 'ShoppingCart.AddCouponCode' method automatically recalculates the shopping cart, 
              // so there is no need to call the Evaluate() method after
              if ((couponCode == "") || !currentCart.AddCouponCode(couponCode))
              {
                  // Adds an error message to the model state if the entered coupon code is not valid
                  ModelState.AddModelError("CouponCodeError", "The entered coupon code is not valid.");                
              }

              // Initializes the shopping cart model
              ShoppingCartViewModel model = new ShoppingCartViewModel
              {
                  // Assigns the current shopping cart to the model
                  Cart = currentCart,
                  RemainingAmountForFreeShipping = pricingService.CalculateRemainingAmountForFreeShipping(currentCart)
              };

              // Displays the shopping cart
              return View("ShoppingCart", model);
          }

          /// <summary>
          /// Removes the specified coupon code from the shopping cart.
          /// </summary>
          [HttpPost]
          public ActionResult RemoveCouponCode(string couponCode)
          {
              // Gets the current user's shopping cart
              ShoppingCart currentCart = shoppingService.GetCurrentShoppingCart();

              // Removes the specified coupon code
              // The 'ShoppingCart.RemoveCouponCode' method automatically recalculates the shopping cart, 
              // so there is no need to call the Evaluate() method after
              currentCart.RemoveCouponCode(couponCode);

              // Displays the shopping cart
              return RedirectToAction("ShoppingCart");
          }

Perform the following changes in your shopping cart view:
1. Create a form with a coupon code text input and an apply button (send POST requests to the action that adds coupon codes).
2. Display applied coupon codes from the AppliedCouponCodes collection of the current shopping cart object.
3. For each applied coupon code, add a form with a single button that allows customers to remove the given coupon code (send POST requests to the action that removes coupon codes).




@* Coupon code text box and apply button *@
@using (Html.BeginForm("AddCouponCode", "Checkout", FormMethod.Post))
{
    <input type="text" name="CouponCode" />
    <input type="submit" value="Apply" />
    @Html.ValidationMessage("CouponCodeError")
}
@* List of applied coupon codes with remove buttons *@
<ul>
    @* Loops through all applied coupon codes *@
    @foreach (string couponCode in Model.Cart.AppliedCouponCodes)
    {
        <li>
            @couponCode

            @using (Html.BeginForm("RemoveCouponCode", "Checkout", FormMethod.Post))
            {
                <input type="hidden" name="CouponCode" value="@couponCode" />
                <input type="submit" value="Remove" />
            }
        </li>
    }
</ul>

The system now accepts coupon codes typed during the checkout process and customers can get their discounts.