Build an E-Commerce Order API with ASP.NET Core

Problem/Feature Description

An e-commerce company needs an order management API built with ASP.NET Core and C#. A Vue.js storefront on https://store.example.com will consume this API. Customers browse products, add items to a cart, and place orders.

The API needs the following endpoints:

• GET /api/products -- list available products (public, supports ?category=electronics&sort=price)
• GET /api/products/{id} -- get product details (public)
• POST /api/orders -- place a new order (authenticated, accepts items array with productId and quantity, plus shippingAddress)
• GET /api/orders -- list the current user's orders (authenticated)
• GET /api/orders/{id} -- get order details (authenticated, users can only see their own orders)
• PATCH /api/orders/{id}/cancel -- cancel an order (authenticated, only if status is "Pending")
• GET /api/admin/orders -- list all orders (admin only, supports ?status=pending&page=1)

Use an in-memory data store. Products have Id, Name, Description, Price, Category, StockQuantity. Orders have Id, UserId, Items, ShippingAddress, Status (Pending, Confirmed, Shipped, Cancelled), Total, CreatedAt.

Output Specification

Produce:

• Program.cs -- Application setup with services and middleware
• Controllers/ProductsController.cs -- Product browsing endpoints
• Controllers/OrdersController.cs -- Order management endpoints
• Models/ -- Request/response DTOs and entity classes
• Services/OrderService.cs -- Order processing business logic
• appsettings.json -- Configuration
• ECommerceApi.csproj -- Project file with NuGet packages