Why should you care?

ShopNest categories organize thousands of products — one-to-many is the backbone of catalog navigation.

See it live — copy this example

Paste into a .NET project with EF Core packages, then run with LocalDB/SQL Server (dotnet ef / dotnet run).

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; } = "";
    public ICollection<Product> Products { get; set; } = new List<Product>();
}

// Fluent:
modelBuilder.Entity<Product>()
    .HasOne(p => p.Category)
    .WithMany(c => c.Products)
    .HasForeignKey(p => p.CategoryId);

What happened?

• CategoryId on Product is FK.
• WithMany on Category completes bidirectional mapping.
• EF creates index on CategoryId automatically.

Practice next

1. Ensure FK property type matches parent PK type.
2. Configure delete behavior — Restrict vs Cascade for categories.
3. Query products by CategoryId with index support.
4. Add required Category on Product — migrate NOT NULL CategoryId.
5. Filter products: _context.Products.Where(p => p.Category!.Name == "Electronics").

Remember

FK on many side points to one parent. ICollection on parent lists children. Configure OnDelete explicitly.

ShopNest category browse

Browse Electronics loads Products where CategoryId matches via indexed FK.

Outcome: Flipkart-style aisle navigation backed by simple one-to-many schema.