Create a new state-driven checkout page

src/Libraries/Nop.Core/Domain/Customers/NopCustomerDefaults.cs

@@ -100,6 +100,8 @@ public static partial class NopCustomerDefaults
     /// </summary>
     public static string SelectedPaymentMethodAttribute => "SelectedPaymentMethod";
 
+    public static string ShipToSameAddressAttribute => "ShipToSameAddress";
+
     /// <summary>
     /// Gets a name of generic attribute to store the value of 'SelectedShippingOption'
     /// </summary>

src/Libraries/Nop.Core/Domain/Orders/OrderSettings.cs

@@ -58,6 +58,8 @@ public partial class OrderSettings : ISettings
     /// </summary>
     public bool OnePageCheckoutEnabled { get; set; }
 
+    public bool SinglePageCheckoutEnabled { get; set; }
+
     /// <summary>
     /// Gets or sets a value indicating whether order totals should be displayed on 'Payment info' tab of 'One-page checkout' page
     /// </summary>

src/Libraries/Nop.Core/Http/NopRouteNames.cs

@@ -131,6 +131,8 @@ public static partial class Standard
         /// </summary>
         public const string CHECKOUT_ONE_PAGE = "CheckoutOnePage";
 
+        public const string CHECKOUT_SINGLE_PAGE = "CheckoutSinglePage";
+
         /// <summary>
         /// Gets the checkout shipping address route name
         /// </summary>

src/Presentation/Nop.Web/Controllers/CheckoutController.cs

@@ -7,6 +7,7 @@
 using Nop.Core.Domain.Payments;
 using Nop.Core.Domain.Security;
 using Nop.Core.Domain.Shipping;
+using Nop.Core.Domain.Stores;
 using Nop.Core.Domain.Tax;
 using Nop.Core.Http;
 using Nop.Services.Attributes;
@@ -382,6 +383,9 @@ public virtual async Task<IActionResult> Index()
         if (_orderSettings.OnePageCheckoutEnabled)
             return RedirectToRoute(NopRouteNames.Standard.CHECKOUT_ONE_PAGE);
 
+        if (_orderSettings.SinglePageCheckoutEnabled)
+            return RedirectToRoute(NopRouteNames.Standard.CHECKOUT_SINGLE_PAGE);
+
         return RedirectToRoute(NopRouteNames.Standard.CHECKOUT_BILLING_ADDRESS);
     }
 
@@ -1723,7 +1727,7 @@ await _checkoutModelFactory.PrepareShippingAddressModelAsync(shippingAddressMode
                             .Select(p => p.ErrorMessage))
                     });
                 }
-
+                
                 //try to find an address with the same values (don't duplicate records)
                 var address = _addressService.FindAddress((await _customerService.GetAddressesByCustomerIdAsync(customer.Id)).ToList(),
                     newAddress.FirstName, newAddress.LastName, newAddress.PhoneNumber,