Why should you care?

ShopNest warehouse bin locations may be unique by WarehouseId + Aisle + Bin — composite keys model natural identifiers without surrogate Id.

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 WarehouseBin
{
    public int WarehouseId { get; set; }
    public string Aisle { get; set; } = "";
    public string BinCode { get; set; } = "";
    public int ProductId { get; set; }
}

// Fluent API:
modelBuilder.Entity<WarehouseBin>()
    .HasKey(b => new { b.WarehouseId, b.Aisle, b.BinCode });

What happened?

• HasKey with anonymous type defines composite PK.
• EF creates clustered index on all three columns.
• FindAsync requires all key parts.

Practice next

1. Identify a natural composite key in ShopNest inventory (e.g., wishlist UserId + ProductId).
2. Configure HasKey and add migration.
3. Try FindAsync with all key values vs missing one.
4. Model OrderItem with composite key OrderId + LineNumber instead of Id.
5. Query by key: _context.WarehouseBins.Find(1, "A", "B12").

Remember

Composite keys combine multiple columns as PK. Configure via Fluent HasKey or [PrimaryKey]. Surrogate keys are often simpler for ORM apps.

ShopNest stock location key

Inventory service uses WarehouseId+Aisle+BinCode composite key to prevent duplicate bin assignments.

Outcome: Natural key matches warehouse labels on physical shelves.