Feature: Add product variant price override support

Enables individual variants to have their own prices, overriding the base product price.

**Database Changes:**
- Added Price (decimal?, nullable) to ProductVariants table
- Added ProductVariantId to OrderItems table with foreign key relationship
- Created index on OrderItems.ProductVariantId for performance

**API Changes:**
- ProductVariantDto: Added Price field
- CreateProductVariantDto: Added Price field with validation
- UpdateProductVariantDto: Added Price field
- OrderItemDto: Added ProductVariantId and ProductVariantName
- CreateOrderItemDto: Added ProductVariantId

**Business Logic:**
- OrderService: Variant price overrides base price (but multi-buy takes precedence)
- ProductService: All variant CRUD operations support Price field

**Admin UI:**
- CreateVariant: Price input with £ symbol and base price placeholder
- EditVariant: Price editing with £ symbol
- ProductVariants list: Shows variant price or "(base)" indicator

**Client Library:**
- Updated all DTOs to match server-side changes
- Full support for variant pricing in order creation

**Migration:**
- EF Core migration: 20251003173458_AddVariantPricing
- Backward compatible: NULL values supported for existing data

**Use Case:**
Products with size/color variants can now have different prices:
- Small T-shirt: £15.00 (variant override)
- Medium T-shirt: £18.00 (uses base price)
- Large T-shirt: £20.00 (variant override)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

LittleShop.Client/Models/Order.cs

@@ -27,7 +27,9 @@ public class OrderItem
 {
     public Guid Id { get; set; }
     public Guid ProductId { get; set; }
+    public Guid? ProductVariantId { get; set; }
     public string? ProductName { get; set; }
+    public string? ProductVariantName { get; set; }
     public int Quantity { get; set; }
     public decimal UnitPrice { get; set; }
     public decimal TotalPrice { get; set; }
@@ -55,6 +57,7 @@ public class CreateOrderItem
 {
     public Guid ProductId { get; set; }
     public Guid? ProductMultiBuyId { get; set; } // Optional: if specified, use multi-buy pricing
-    public string? SelectedVariant { get; set; } // Optional: variant choice (color/flavor)
+    public Guid? ProductVariantId { get; set; } // Optional: specific variant (used for variant price override)
+    public string? SelectedVariant { get; set; } // Optional: variant choice (color/flavor) - deprecated, use ProductVariantId
     public int Quantity { get; set; }
 }

LittleShop.Client/Models/Product.cs

@@ -49,5 +49,6 @@ public class ProductVariant
     public int StockLevel { get; set; }
     public decimal? Weight { get; set; }  // Optional: override product weight
     public int? WeightUnit { get; set; }  // Optional: override product weight unit
+    public decimal? Price { get; set; }  // Optional: override product price (if null, uses product.Price)
     public bool IsActive { get; set; }
 }

LittleShop/Areas/Admin/Views/Products/CreateVariant.cshtml

@@ -55,6 +55,16 @@
                         <small class="form-text text-muted">Track inventory for this specific variant (optional)</small>
                     </div>
 
+                    <div class="mb-3">
+                        <label asp-for="Price" class="form-label"></label>
+                        <div class="input-group">
+                            <span class="input-group-text">£</span>
+                            <input asp-for="Price" type="number" step="0.01" class="form-control" min="0.01" placeholder="@product?.Price.ToString("F2")" />
+                        </div>
+                        <span asp-validation-for="Price" class="text-danger"></span>
+                        <small class="form-text text-muted">Override base price for this variant (optional - defaults to £@product?.Price.ToString("F2"))</small>
+                    </div>
+
                     <div class="mb-3">
                         <label asp-for="SortOrder" class="form-label"></label>
                         <input asp-for="SortOrder" type="number" class="form-control" />

LittleShop/Areas/Admin/Views/Products/EditVariant.cshtml

@@ -51,6 +51,16 @@
                         <span asp-validation-for="StockLevel" class="text-danger"></span>
                     </div>
 
+                    <div class="mb-3">
+                        <label asp-for="Price" class="form-label"></label>
+                        <div class="input-group">
+                            <span class="input-group-text">£</span>
+                            <input asp-for="Price" type="number" step="0.01" class="form-control" min="0.01" placeholder="@product?.Price.ToString("F2")" />
+                        </div>
+                        <span asp-validation-for="Price" class="text-danger"></span>
+                        <small class="form-text text-muted">Override base price (optional - defaults to £@product?.Price.ToString("F2"))</small>
+                    </div>
+
                     <div class="mb-3">
                         <label asp-for="SortOrder" class="form-label"></label>
                         <input asp-for="SortOrder" type="number" class="form-control" />

LittleShop/Areas/Admin/Views/Products/ProductVariants.cshtml

@@ -33,6 +33,7 @@
                         <tr>
                             <th>Name</th>
                             <th>Type</th>
+                            <th>Price</th>
                             <th>Stock Level</th>
                             <th>Sort Order</th>
                             <th>Status</th>
@@ -49,6 +50,16 @@
                                 <td>
                                     <span class="badge bg-info">@variant.VariantType</span>
                                 </td>
+                                <td>
+                                    @if (variant.Price.HasValue)
+                                    {
+                                        <strong>£@variant.Price.Value.ToString("F2")</strong>
+                                    }
+                                    else
+                                    {
+                                        <span class="text-muted">£@product?.Price.ToString("F2") (base)</span>
+                                    }
+                                </td>
                                 <td>
                                     @if (variant.StockLevel > 0)
                                     {

LittleShop/DTOs/OrderDto.cs

@@ -51,8 +51,10 @@ public class OrderItemDto
     public Guid Id { get; set; }
     public Guid ProductId { get; set; }
     public Guid? ProductMultiBuyId { get; set; }
+    public Guid? ProductVariantId { get; set; }
     public string ProductName { get; set; } = string.Empty;
     public string? ProductMultiBuyName { get; set; }
+    public string? ProductVariantName { get; set; }
     public string? SelectedVariant { get; set; }
     public int Quantity { get; set; }
     public decimal UnitPrice { get; set; }
@@ -97,7 +99,9 @@ public class CreateOrderItemDto
 
     public Guid? ProductMultiBuyId { get; set; } // Optional: if specified, use multi-buy pricing
 
-    public string? SelectedVariant { get; set; } // Optional: variant choice (color/flavor)
+    public Guid? ProductVariantId { get; set; } // Optional: specific variant (used for variant price override)
+
+    public string? SelectedVariant { get; set; } // Optional: variant choice (color/flavor) - deprecated, use ProductVariantId
 
     [Range(1, int.MaxValue)]
     public int Quantity { get; set; }

LittleShop/DTOs/ProductDto.cs

@@ -125,6 +125,7 @@ public class ProductVariantDto
     public string VariantType { get; set; } = "Standard";
     public int SortOrder { get; set; }
     public int StockLevel { get; set; }
+    public decimal? Price { get; set; } // If null, uses product.Price
     public bool IsActive { get; set; }
     public DateTime CreatedAt { get; set; }
     public DateTime UpdatedAt { get; set; }
@@ -170,6 +171,9 @@ public class CreateProductVariantDto
 
     [Range(0, int.MaxValue)]
     public int StockLevel { get; set; } = 0;
+
+    [Range(0.01, double.MaxValue, ErrorMessage = "Price must be greater than 0")]
+    public decimal? Price { get; set; } // Optional: If null, uses product.Price
 }
 
 public class UpdateProductMultiBuyDto
@@ -205,5 +209,8 @@ public class UpdateProductVariantDto
     [Range(0, int.MaxValue)]
     public int? StockLevel { get; set; }
 
+    [Range(0.01, double.MaxValue, ErrorMessage = "Price must be greater than 0")]
+    public decimal? Price { get; set; } // Optional: If null, uses product.Price
+
     public bool? IsActive { get; set; }
 }

LittleShop/Migrations/20251003173458_AddVariantPricing.cs

@@ -0,0 +1,59 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace LittleShop.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddVariantPricing : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<decimal>(
+                name: "Price",
+                table: "ProductVariants",
+                type: "TEXT",
+                nullable: true);
+
+            migrationBuilder.AddColumn<Guid>(
+                name: "ProductVariantId",
+                table: "OrderItems",
+                type: "TEXT",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_OrderItems_ProductVariantId",
+                table: "OrderItems",
+                column: "ProductVariantId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_OrderItems_ProductVariants_ProductVariantId",
+                table: "OrderItems",
+                column: "ProductVariantId",
+                principalTable: "ProductVariants",
+                principalColumn: "Id");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_OrderItems_ProductVariants_ProductVariantId",
+                table: "OrderItems");
+
+            migrationBuilder.DropIndex(
+                name: "IX_OrderItems_ProductVariantId",
+                table: "OrderItems");
+
+            migrationBuilder.DropColumn(
+                name: "Price",
+                table: "ProductVariants");
+
+            migrationBuilder.DropColumn(
+                name: "ProductVariantId",
+                table: "OrderItems");
+        }
+    }
+}

LittleShop/Migrations/LittleShopContextModelSnapshot.cs

@@ -859,6 +859,9 @@ namespace LittleShop.Migrations
                     b.Property<Guid?>("ProductMultiBuyId")
                         .HasColumnType("TEXT");
 
+                    b.Property<Guid?>("ProductVariantId")
+                        .HasColumnType("TEXT");
+
                     b.Property<int>("Quantity")
                         .HasColumnType("INTEGER");
 
@@ -880,6 +883,8 @@ namespace LittleShop.Migrations
 
                     b.HasIndex("ProductMultiBuyId");
 
+                    b.HasIndex("ProductVariantId");
+
                     b.ToTable("OrderItems");
                 });
 
@@ -1041,6 +1046,9 @@ namespace LittleShop.Migrations
                         .HasMaxLength(100)
                         .HasColumnType("TEXT");
 
+                    b.Property<decimal?>("Price")
+                        .HasColumnType("TEXT");
+
                     b.Property<Guid>("ProductId")
                         .HasColumnType("TEXT");
 
@@ -1537,11 +1545,17 @@ namespace LittleShop.Migrations
                         .HasForeignKey("ProductMultiBuyId")
                         .OnDelete(DeleteBehavior.Restrict);
 
+                    b.HasOne("LittleShop.Models.ProductVariant", "ProductVariant")
+                        .WithMany()
+                        .HasForeignKey("ProductVariantId");
+
                     b.Navigation("Order");
 
                     b.Navigation("Product");
 
                     b.Navigation("ProductMultiBuy");
+
+                    b.Navigation("ProductVariant");
                 });
 
             modelBuilder.Entity("LittleShop.Models.Product", b =>

LittleShop/Models/OrderItem.cs

@@ -14,6 +14,8 @@ public class OrderItem
 
     public Guid? ProductMultiBuyId { get; set; } // Nullable for backward compatibility
 
+    public Guid? ProductVariantId { get; set; } // Optional: specific variant with potential price override
+
     [StringLength(500)]
     public string? SelectedVariants { get; set; } // JSON array of variants chosen (e.g., ["Red", "Blue", "Green"] for multi-buy)
 
@@ -29,4 +31,5 @@ public class OrderItem
     public virtual Order Order { get; set; } = null!;
     public virtual Product Product { get; set; } = null!;
     public virtual ProductMultiBuy? ProductMultiBuy { get; set; }
+    public virtual ProductVariant? ProductVariant { get; set; }
 }

LittleShop/Models/ProductVariant.cs

@@ -27,6 +27,8 @@ public class ProductVariant
 
     public ProductWeightUnit? WeightUnit { get; set; } // Optional: override product weight unit for this variant
 
+    public decimal? Price { get; set; } // Optional: override product price for this variant (if null, uses product.Price)
+
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 
     public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;

LittleShop/Services/OrderService.cs

@@ -78,6 +78,8 @@ public class OrderService : IOrderService
             .ThenInclude(oi => oi.Product)
             .Include(o => o.Items)
             .ThenInclude(oi => oi.ProductMultiBuy)
+            .Include(o => o.Items)
+            .ThenInclude(oi => oi.ProductVariant)
             .Include(o => o.Payments)
             .FirstOrDefaultAsync(o => o.Id == id);
 
@@ -147,8 +149,25 @@ public class OrderService : IOrderService
                 }
 
                 ProductMultiBuy? multiBuy = null;
+                ProductVariant? variant = null;
                 decimal unitPrice = product.Price;
 
+                // Check for variant price override (highest priority after multi-buy)
+                if (itemDto.ProductVariantId.HasValue)
+                {
+                    variant = await _context.ProductVariants.FindAsync(itemDto.ProductVariantId.Value);
+                    if (variant == null || !variant.IsActive || variant.ProductId != itemDto.ProductId)
+                    {
+                        throw new ArgumentException($"Product variant {itemDto.ProductVariantId} not found, inactive, or doesn't belong to product {itemDto.ProductId}");
+                    }
+
+                    // Use variant price if it has an override, otherwise use product base price
+                    if (variant.Price.HasValue)
+                    {
+                        unitPrice = variant.Price.Value;
+                    }
+                }
+
                 if (itemDto.ProductMultiBuyId.HasValue)
                 {
                     multiBuy = await _context.ProductMultiBuys.FindAsync(itemDto.ProductMultiBuyId.Value);
@@ -168,6 +187,7 @@ public class OrderService : IOrderService
                     OrderId = order.Id,
                     ProductId = itemDto.ProductId,
                     ProductMultiBuyId = itemDto.ProductMultiBuyId,
+                    ProductVariantId = itemDto.ProductVariantId,
                     Quantity = itemDto.Quantity,
                     UnitPrice = unitPrice,
                     TotalPrice = unitPrice * itemDto.Quantity
@@ -331,8 +351,10 @@ public class OrderService : IOrderService
                 Id = oi.Id,
                 ProductId = oi.ProductId,
                 ProductMultiBuyId = oi.ProductMultiBuyId,
+                ProductVariantId = oi.ProductVariantId,
                 ProductName = oi.Product.Name,
                 ProductMultiBuyName = oi.ProductMultiBuy?.Name,
+                ProductVariantName = oi.ProductVariant?.Name,
                 Quantity = oi.Quantity,
                 UnitPrice = oi.UnitPrice,
                 TotalPrice = oi.TotalPrice

LittleShop/Services/ProductService.cs

@@ -556,6 +556,7 @@ public class ProductService : IProductService
             VariantType = createVariantDto.VariantType,
             SortOrder = createVariantDto.SortOrder,
             StockLevel = createVariantDto.StockLevel,
+            Price = createVariantDto.Price,
             IsActive = true,
             CreatedAt = DateTime.UtcNow,
             UpdatedAt = DateTime.UtcNow
@@ -572,6 +573,7 @@ public class ProductService : IProductService
             VariantType = variant.VariantType,
             SortOrder = variant.SortOrder,
             StockLevel = variant.StockLevel,
+            Price = variant.Price,
             IsActive = variant.IsActive,
             CreatedAt = variant.CreatedAt,
             UpdatedAt = variant.UpdatedAt
@@ -595,6 +597,9 @@ public class ProductService : IProductService
         if (updateVariantDto.StockLevel.HasValue)
             variant.StockLevel = updateVariantDto.StockLevel.Value;
 
+        if (updateVariantDto.Price.HasValue)
+            variant.Price = updateVariantDto.Price.Value;
+
         if (updateVariantDto.IsActive.HasValue)
             variant.IsActive = updateVariantDto.IsActive.Value;
 
@@ -627,6 +632,7 @@ public class ProductService : IProductService
                 VariantType = v.VariantType,
                 SortOrder = v.SortOrder,
                 StockLevel = v.StockLevel,
+                Price = v.Price,
                 IsActive = v.IsActive,
                 CreatedAt = v.CreatedAt,
                 UpdatedAt = v.UpdatedAt
@@ -647,6 +653,7 @@ public class ProductService : IProductService
             VariantType = variant.VariantType,
             SortOrder = variant.SortOrder,
             StockLevel = variant.StockLevel,
+            Price = variant.Price,
             IsActive = variant.IsActive,
             CreatedAt = variant.CreatedAt,
             UpdatedAt = variant.UpdatedAt