entity-design

Entity Design (EF Core)

Design and configure EF Core entities following project conventions.

Workflow

1. Define the entity class with properties and base class inheritance
2. Add navigation properties for relationships
3. Create IEntityTypeConfiguration<T> with Fluent API configuration
4. Register in DbContext via OnModelCreating or assembly scanning
5. Generate and review migration to verify the resulting schema

Entity Structure

public class Invoice : EntityBase
{
    public string InvoiceNumber { get; set; } = string.Empty;
    public decimal Total { get; set; }
    public InvoiceStatus Status { get; set; }

    // Navigation properties
    public Guid CustomerId { get; set; }
    public Customer Customer { get; set; } = null!;
    public ICollection<InvoiceLineItem> LineItems { get; set; } = new List<InvoiceLineItem>();
}

Configuration

public class InvoiceConfiguration : IEntityTypeConfiguration<Invoice>
{
    public void Configure(EntityTypeBuilder<Invoice> builder)
    {
        builder.HasKey(x => x.Id);
        builder.Property(x => x.InvoiceNumber).HasMaxLength(50).IsRequired();
        builder.Property(x => x.Total).HasPrecision(18, 2);

        builder.HasOne(x => x.Customer)
            .WithMany(c => c.Invoices)
            .HasForeignKey(x => x.CustomerId)
            .OnDelete(DeleteBehavior.Restrict);

        builder.HasMany(x => x.LineItems)
            .WithOne(li => li.Invoice)
            .HasForeignKey(li => li.InvoiceId)
            .OnDelete(DeleteBehavior.Cascade);

        // Concurrency token
        builder.Property<byte[]>("RowVersion").IsRowVersion();
    }
}

Best Practices

• Fluent API over data annotations for complex mappings — keeps entities clean
• Owned types for value objects (e.g., Address, Money) — builder.OwnsOne(x => x.Address)
• Shadow properties for audit fields (CreatedAt, ModifiedAt) via SaveChanges override
• Explicit cascade delete — always configure OnDelete() to avoid surprise cascades
• Concurrency tokens — add [Timestamp] or IsRowVersion() for entities edited concurrently