[PR-for-TASK] Implement C# POCO data model for eCommerce catalog and order system with Entity Framework

ECommerceDataModel/Data/ECommerceDbContext.cs

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+using Microsoft.EntityFrameworkCore;
+using ECommerceDataModel.Models;
+
+namespace ECommerceDataModel.Data;
+
+public class ECommerceDbContext : DbContext
+{
+    public DbSet<Category> Categories { get; set; }
+    public DbSet<Product> Products { get; set; }
+    public DbSet<Customer> Customers { get; set; }
+    public DbSet<Order> Orders { get; set; }
+    public DbSet<OrderItem> OrderItems { get; set; }
+
+    public ECommerceDbContext(DbContextOptions<ECommerceDbContext> options) : base(options)
+    {
+    }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(modelBuilder);
+
+        // Configure Category entity
+        modelBuilder.Entity<Category>(entity =>
+        {
+            entity.HasKey(e => e.Id);
+            entity.HasIndex(e => e.Name).IsUnique();
+            entity.Property(e => e.Name).IsRequired().HasMaxLength(100);
+            entity.Property(e => e.Description).HasMaxLength(500);
+        });
+
+        // Configure Product entity
+        modelBuilder.Entity<Product>(entity =>
+        {
+            entity.HasKey(e => e.Id);
+            entity.HasIndex(e => e.SKU).IsUnique();
+            entity.Property(e => e.Name).IsRequired().HasMaxLength(200);
+            entity.Property(e => e.Description).HasMaxLength(1000);
+            entity.Property(e => e.Price).HasColumnType("decimal(18,2)").IsRequired();
+            entity.Property(e => e.StockQuantity).IsRequired();
+            entity.Property(e => e.SKU).HasMaxLength(50);
+            entity.Property(e => e.IsActive).HasDefaultValue(true);
+            entity.Property(e => e.CreatedDate).HasDefaultValueSql("GETUTCDATE()");
+
+            // Foreign key relationship
+            entity.HasOne(p => p.Category)
+                  .WithMany(c => c.Products)
+                  .HasForeignKey(p => p.CategoryId)
+                  .OnDelete(DeleteBehavior.Restrict);
+        });
+
+        // Configure Customer entity
+        modelBuilder.Entity<Customer>(entity =>
+        {
+            entity.HasKey(e => e.Id);
+            entity.HasIndex(e => e.Email).IsUnique();
+            entity.Property(e => e.FirstName).IsRequired().HasMaxLength(100);
+            entity.Property(e => e.LastName).IsRequired().HasMaxLength(100);
+            entity.Property(e => e.Email).IsRequired().HasMaxLength(255);
+            entity.Property(e => e.Phone).HasMaxLength(20);
+            entity.Property(e => e.Address).HasMaxLength(255);
+            entity.Property(e => e.City).HasMaxLength(100);
+            entity.Property(e => e.PostalCode).HasMaxLength(10);
+            entity.Property(e => e.Country).HasMaxLength(100);
+            entity.Property(e => e.CreatedDate).HasDefaultValueSql("GETUTCDATE()");
+        });
+
+        // Configure Order entity
+        modelBuilder.Entity<Order>(entity =>
+        {
+            entity.HasKey(e => e.Id);
+            entity.HasIndex(e => e.OrderNumber).IsUnique();
+            entity.Property(e => e.OrderNumber).IsRequired().HasMaxLength(50);
+            entity.Property(e => e.OrderDate).HasDefaultValueSql("GETUTCDATE()");
+            entity.Property(e => e.TotalAmount).HasColumnType("decimal(18,2)").IsRequired();
+            entity.Property(e => e.Status).IsRequired().HasMaxLength(50).HasDefaultValue("Pending");
+            entity.Property(e => e.ShippingAddress).HasMaxLength(255);
+            entity.Property(e => e.ShippingCity).HasMaxLength(100);
+            entity.Property(e => e.ShippingPostalCode).HasMaxLength(10);
+            entity.Property(e => e.ShippingCountry).HasMaxLength(100);
+
+            // Foreign key relationship
+            entity.HasOne(o => o.Customer)
+                  .WithMany(c => c.Orders)
+                  .HasForeignKey(o => o.CustomerId)
+                  .OnDelete(DeleteBehavior.Restrict);
+        });
+
+        // Configure OrderItem entity
+        modelBuilder.Entity<OrderItem>(entity =>
+        {
+            entity.HasKey(e => e.Id);
+            entity.Property(e => e.Quantity).IsRequired();
+            entity.Property(e => e.UnitPrice).HasColumnType("decimal(18,2)").IsRequired();
+            entity.Property(e => e.TotalPrice).HasColumnType("decimal(18,2)").IsRequired();
+
+            // Foreign key relationships
+            entity.HasOne(oi => oi.Order)
+                  .WithMany(o => o.OrderItems)
+                  .HasForeignKey(oi => oi.OrderId)
+                  .OnDelete(DeleteBehavior.Cascade);
+
+            entity.HasOne(oi => oi.Product)
+                  .WithMany(p => p.OrderItems)
+                  .HasForeignKey(oi => oi.ProductId)
+                  .OnDelete(DeleteBehavior.Restrict);
+
+            // Composite index for performance
+            entity.HasIndex(e => new { e.OrderId, e.ProductId });
+        });
+
+        // Seed data
+        SeedData(modelBuilder);
+    }
+
+    private static void SeedData(ModelBuilder modelBuilder)
+    {
+        // Seed Categories
+        modelBuilder.Entity<Category>().HasData(
+            new Category { Id = 1, Name = "Electronics", Description = "Electronic devices and accessories" },
+            new Category { Id = 2, Name = "Clothing", Description = "Fashion and apparel" },
+            new Category { Id = 3, Name = "Books", Description = "Books and educational materials" }
+        );
+
+        // Seed Products
+        modelBuilder.Entity<Product>().HasData(
+            new Product { Id = 1, Name = "Laptop", Description = "High-performance laptop", Price = 999.99m, StockQuantity = 50, SKU = "LAP001", CategoryId = 1 },
+            new Product { Id = 2, Name = "Smartphone", Description = "Latest smartphone model", Price = 699.99m, StockQuantity = 100, SKU = "PHN001", CategoryId = 1 },
+            new Product { Id = 3, Name = "T-Shirt", Description = "Cotton t-shirt", Price = 19.99m, StockQuantity = 200, SKU = "TSH001", CategoryId = 2 },
+            new Product { Id = 4, Name = "Programming Book", Description = "Learn C# programming", Price = 49.99m, StockQuantity = 75, SKU = "BK001", CategoryId = 3 }
+        );
+
+        // Seed Customer
+        modelBuilder.Entity<Customer>().HasData(
+            new Customer { Id = 1, FirstName = "John", LastName = "Doe", Email = "john.doe@example.com", Phone = "123-456-7890", Address = "123 Main St", City = "Anytown", PostalCode = "12345", Country = "USA" }
+        );
+    }
+}

ECommerceDataModel/ECommerceDataModel.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.9" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="9.0.9" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.0.9" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="9.0.9">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+</Project>

ECommerceDataModel/ERD.md

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+# eCommerce Data Model - Entity Relationship Diagram
+
+```
+┌─────────────────┐         ┌─────────────────┐
+│     Category    │         │     Customer    │
+├─────────────────┤         ├─────────────────┤
+│ Id (PK)         │         │ Id (PK)         │
+│ Name            │         │ FirstName       │
+│ Description     │         │ LastName        │
+└─────────────────┘         │ Email           │
+         │                  │ Phone           │
+         │ 1:N              │ Address         │
+         ▼                  │ City            │
+┌─────────────────┐         │ PostalCode      │
+│     Product     │         │ Country         │
+├─────────────────┤         │ CreatedDate     │
+│ Id (PK)         │         └─────────────────┘
+│ Name            │                  │
+│ Description     │                  │ 1:N
+│ Price           │                  ▼
+│ StockQuantity   │         ┌─────────────────┐
+│ SKU             │         │      Order      │
+│ IsActive        │         ├─────────────────┤
+│ CreatedDate     │         │ Id (PK)         │
+│ CategoryId (FK) │         │ OrderNumber     │
+└─────────────────┘         │ OrderDate       │
+         │                  │ TotalAmount     │
+         │ N:M              │ Status          │
+         │ (via OrderItem)  │ ShippingAddress │
+         ▼                  │ ShippingCity    │
+┌─────────────────┐         │ ShippingPostalCode │
+│    OrderItem    │         │ ShippingCountry │
+├─────────────────┤         │ ShippedDate     │
+│ Id (PK)         │         │ DeliveredDate   │
+│ Quantity        │         │ CustomerId (FK) │
+│ UnitPrice       │         └─────────────────┘
+│ TotalPrice      │                  ▲
+│ OrderId (FK)    │                  │ 1:N
+│ ProductId (FK)  │                  │
+└─────────────────┘──────────────────┘
+```
+
+## Relationships:
+
+1. **Category → Product** (1:N)
+   - One category can have many products
+   - Each product belongs to one category
+
+2. **Customer → Order** (1:N)
+   - One customer can place many orders
+   - Each order belongs to one customer
+
+3. **Order → OrderItem** (1:N)
+   - One order can have many order items
+   - Each order item belongs to one order
+
+4. **Product → OrderItem** (1:N)
+   - One product can appear in many order items
+   - Each order item references one product
+
+5. **Product ↔ Order** (N:M via OrderItem)
+   - Many-to-many relationship through OrderItem junction table
+   - Allows tracking quantity and pricing per order
+
+## Key Constraints:
+
+- **Unique Indexes**: Category.Name, Product.SKU, Customer.Email, Order.OrderNumber
+- **Foreign Key Constraints**: All relationships enforced with restrict/cascade rules
+- **Data Validation**: Required fields, max lengths, email format validation
+- **Default Values**: Timestamps, boolean flags, status fields

ECommerceDataModel/Models/Category.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace ECommerceDataModel.Models;
+
+public class Category
+{
+    public int Id { get; set; }
+
+    [Required]
+    [MaxLength(100)]
+    public string Name { get; set; } = string.Empty;
+
+    [MaxLength(500)]
+    public string? Description { get; set; }
+
+    // Navigation property
+    public virtual ICollection<Product> Products { get; set; } = new List<Product>();
+}

ECommerceDataModel/Models/Customer.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace ECommerceDataModel.Models;
+
+public class Customer
+{
+    public int Id { get; set; }
+
+    [Required]
+    [MaxLength(100)]
+    public string FirstName { get; set; } = string.Empty;
+
+    [Required]
+    [MaxLength(100)]
+    public string LastName { get; set; } = string.Empty;
+
+    [Required]
+    [MaxLength(255)]
+    [EmailAddress]
+    public string Email { get; set; } = string.Empty;
+
+    [MaxLength(20)]
+    public string? Phone { get; set; }
+
+    [MaxLength(255)]
+    public string? Address { get; set; }
+
+    [MaxLength(100)]
+    public string? City { get; set; }
+
+    [MaxLength(10)]
+    public string? PostalCode { get; set; }
+
+    [MaxLength(100)]
+    public string? Country { get; set; }
+
+    public DateTime CreatedDate { get; set; } = DateTime.UtcNow;
+
+    // Navigation property
+    public virtual ICollection<Order> Orders { get; set; } = new List<Order>();
+}

ECommerceDataModel/Models/Order.cs

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+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace ECommerceDataModel.Models;
+
+public class Order
+{
+    public int Id { get; set; }
+
+    [Required]
+    [MaxLength(50)]
+    public string OrderNumber { get; set; } = string.Empty;
+
+    public DateTime OrderDate { get; set; } = DateTime.UtcNow;
+
+    [Required]
+    [Column(TypeName = "decimal(18,2)")]
+    public decimal TotalAmount { get; set; }
+
+    [Required]
+    [MaxLength(50)]
+    public string Status { get; set; } = "Pending"; // Pending, Processing, Shipped, Delivered, Cancelled
+
+    [MaxLength(255)]
+    public string? ShippingAddress { get; set; }
+
+    [MaxLength(100)]
+    public string? ShippingCity { get; set; }
+
+    [MaxLength(10)]
+    public string? ShippingPostalCode { get; set; }
+
+    [MaxLength(100)]
+    public string? ShippingCountry { get; set; }
+
+    public DateTime? ShippedDate { get; set; }
+
+    public DateTime? DeliveredDate { get; set; }
+
+    // Foreign key
+    public int CustomerId { get; set; }
+
+    // Navigation properties
+    public virtual Customer Customer { get; set; } = null!;
+    public virtual ICollection<OrderItem> OrderItems { get; set; } = new List<OrderItem>();
+}

ECommerceDataModel/Models/OrderItem.cs

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+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace ECommerceDataModel.Models;
+
+public class OrderItem
+{
+    public int Id { get; set; }
+
+    [Required]
+    public int Quantity { get; set; }
+
+    [Required]
+    [Column(TypeName = "decimal(18,2)")]
+    public decimal UnitPrice { get; set; }
+
+    [Required]
+    [Column(TypeName = "decimal(18,2)")]
+    public decimal TotalPrice { get; set; }
+
+    // Foreign keys
+    public int OrderId { get; set; }
+    public int ProductId { get; set; }
+
+    // Navigation properties
+    public virtual Order Order { get; set; } = null!;
+    public virtual Product Product { get; set; } = null!;
+}