如何在NopCommerce中实现动作过滤器

我想更改CheckoutController中OpcSaveBilling操作中的一些代码。我不想更改NopCommerce的核心代码，所以我需要尝试用我自己的自定义代码来覆盖代码。

我读这篇文章是为了入门http://www.pronopcommerce.com/overriding-intercepting-nopcommerce-controllers-and-actions.根据我所读到的内容，您可以在执行操作之前和之后执行自己的代码。但我没有得到的是文章中开放的部分（需要执行的实际代码）。

我基本上想要的是与原始代码相同的功能，但有一些自定义的调整。我在OnePageCheckout视图中添加了一个复选框，基于该复选框，它需要跳过结账中的输入发货地址部分。（使用发货地址的账单地址）

我已经在核心代码中添加了该代码，这项工作可以跳过这一步（注意：我知道我仍然需要手动添加账单地址作为发货地址），但正如我所说，我不想更改NopCommerce核心中的代码，而是覆盖它。

如果我的问题无法理解，并且您需要更多的代码或解释，我很乐意提供更多。如果我做这件事的方式不适合我想要的，如果你告诉我，我将不胜感激！

我的代码：

Action Filter类：

using Nop.Web.Controllers;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web.Mvc;
namespace Nop.Plugin.Misc.MyProject.ActionFilters
{
class ShippingAddressOverideActionFilter : ActionFilterAttribute, IFilterProvider
{
    public IEnumerable<Filter> GetFilters(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
    {
        if (controllerContext.Controller is CheckoutController && actionDescriptor.ActionName.Equals("OpcSaveBilling", StringComparison.InvariantCultureIgnoreCase))
        {
            return new List<Filter>() { new Filter(this, FilterScope.Action, 0) };
        }
        return new List<Filter>();
    }
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // What do I put in here? So that I have the code of the core action but with my custom tweaks in it
    }
}

}

在DependencyRegister中的同一个Nop插件中注册了该类

 builder.RegisterType<ShippingAddressOverideActionFilter>().As<System.Web.Mvc.IFilterProvider>();

一个包含自定义代码的工作示例。但这是核心操作。

  public ActionResult OpcSaveBilling(FormCollection form)
    {
        try
        {
            //validation
            var cart = _workContext.CurrentCustomer.ShoppingCartItems
                .Where(sci => sci.ShoppingCartType == ShoppingCartType.ShoppingCart)
            .Where(sci => sci.StoreId == _storeContext.CurrentStore.Id)
                .ToList();
            if (cart.Count == 0)
                throw new Exception("Your cart is empty");
            if (!UseOnePageCheckout())
                throw new Exception("One page checkout is disabled");
            if ((_workContext.CurrentCustomer.IsGuest() && !_orderSettings.AnonymousCheckoutAllowed))
                throw new Exception("Anonymous checkout is not allowed");
            int billingAddressId = 0;
            int.TryParse(form["billing_address_id"], out billingAddressId);

            if (billingAddressId > 0)
            {
                //existing address
                var address = _workContext.CurrentCustomer.Addresses.FirstOrDefault(a => a.Id == billingAddressId);
                if (address == null)
                    throw new Exception("Address can't be loaded");
                _workContext.CurrentCustomer.BillingAddress = address;
                _customerService.UpdateCustomer(_workContext.CurrentCustomer);
            }
            else
            {
                //new address
                var model = new CheckoutBillingAddressModel();
                TryUpdateModel(model.NewAddress, "BillingNewAddress");
                //validate model
                TryValidateModel(model.NewAddress);
                if (!ModelState.IsValid)
                {
                    //model is not valid. redisplay the form with errors
                    var billingAddressModel = PrepareBillingAddressModel(selectedCountryId: model.NewAddress.CountryId);
                    billingAddressModel.NewAddressPreselected = true;
                    return Json(new
                    {
                        update_section = new UpdateSectionJsonModel()
                        {
                            name = "billing",
                            html = this.RenderPartialViewToString("OpcBillingAddress", billingAddressModel)
                        },
                        wrong_billing_address = true,
                    });
                }
                //try to find an address with the same values (don't duplicate records)
                var address = _workContext.CurrentCustomer.Addresses.ToList().FindAddress(
                    model.NewAddress.FirstName, model.NewAddress.LastName, model.NewAddress.PhoneNumber,
                    model.NewAddress.Email, model.NewAddress.FaxNumber, model.NewAddress.Company,
                    model.NewAddress.Address1, model.NewAddress.Address2, model.NewAddress.City,
                    model.NewAddress.StateProvinceId, model.NewAddress.ZipPostalCode, model.NewAddress.CountryId);
                if (address == null)
                {
                    //address is not found. let's create a new one
                    address = model.NewAddress.ToEntity();
                    address.CreatedOnUtc = DateTime.UtcNow;
                    //some validation
                    if (address.CountryId == 0)
                        address.CountryId = null;
                    if (address.StateProvinceId == 0)
                        address.StateProvinceId = null;
                    if (address.CountryId.HasValue && address.CountryId.Value > 0)
                    {
                        address.Country = _countryService.GetCountryById(address.CountryId.Value);
                    }
                    _workContext.CurrentCustomer.Addresses.Add(address);
                }
                _workContext.CurrentCustomer.BillingAddress = address;
                _customerService.UpdateCustomer(_workContext.CurrentCustomer);
            }
            // Get value of checkbox from the one page checkout view
            var useSameAddress = false;
            Boolean.TryParse(form["billing-address-same"], out useSameAddress);
            // If it is checked copy the billing address to shipping address and skip the shipping address part of the checkout
            if (useSameAddress)
            {
                var shippingMethodModel = PrepareShippingMethodModel(cart);
                return Json(new
                {
                    update_section = new UpdateSectionJsonModel()
                    {
                        name = "shipping-method",
                        html = this.RenderPartialViewToString("OpcShippingMethods", shippingMethodModel)
                    },
                    goto_section = "shipping_method"
                });
            }
            // If it isn't checked go to the enter shipping address part of the checkout
            else
            {
                if (cart.RequiresShipping())
                {
                    //shipping is required
                    var shippingAddressModel = PrepareShippingAddressModel(prePopulateNewAddressWithCustomerFields: true);
                    return Json(new
                    {
                        update_section = new UpdateSectionJsonModel()
                        {
                            name = "shipping",
                            html = this.RenderPartialViewToString("OpcShippingAddress", shippingAddressModel)
                        },
                        goto_section = "shipping"
                    });
                }
                else
                {
                    //shipping is not required
                    _genericAttributeService.SaveAttribute<ShippingOption>(_workContext.CurrentCustomer, SystemCustomerAttributeNames.SelectedShippingOption, null, _storeContext.CurrentStore.Id);
                    //load next step
                    return OpcLoadStepAfterShippingMethod(cart);
                }
            }
        }
        catch (Exception exc)
        {
            _logger.Warning(exc.Message, exc, _workContext.CurrentCustomer);
            return Json(new { error = 1, message = exc.Message });
        }
    }

public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // What do I put in here? So that I have the code of the core action but with my custom tweaks in it
    }

filterContext.Result = new RedirectToRouteResult("HomePage", null);