EF Core Configuration Generator

Overview

This skill generates Entity Framework Core configurations using Fluent API:

• IEntityTypeConfiguration<T> - Per-entity configuration classes
• Fluent API over attributes - Keep domain clean
• Snake case naming - PostgreSQL convention
• Relationships - One-to-Many, Many-to-Many, One-to-One
• Value Objects - Owned types mapping

Quick Reference

Configuration Structure

/Infrastructure/Configurations/
├── {Entity}Configuration.cs
├── {ChildEntity}Configuration.cs
├── {ValueObject}Configuration.cs
└── OutboxMessageConfiguration.cs

Template: Basic Entity Configuration

// src/{name}.infrastructure/Configurations/{Entity}Configuration.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using {name}.domain.{aggregate};

namespace {name}.infrastructure.configurations;

internal sealed class {Entity}Configuration : IEntityTypeConfiguration<{Entity}>
{
    public void Configure(EntityTypeBuilder<{Entity}> builder)
    {
        // ═══════════════════════════════════════════════════════════════
        // TABLE MAPPING
        // ═══════════════════════════════════════════════════════════════
        builder.ToTable("{entity}");  // snake_case table name

        // ═══════════════════════════════════════════════════════════════
        // PRIMARY KEY
        // ═══════════════════════════════════════════════════════════════
        builder.HasKey(e => e.Id);
        
        builder.Property(e => e.Id)
            .ValueGeneratedNever();  // App generates GUIDs

        // ═══════════════════════════════════════════════════════════════
        // PROPERTIES
        // ═══════════════════════════════════════════════════════════════
        builder.Property(e => e.Name)
            .HasMaxLength(100)
            .IsRequired();

        builder.Property(e => e.Description)
            .HasColumnType("text");  // Unlimited length

        builder.Property(e => e.IsActive)
            .HasDefaultValue(true)
            .IsRequired();

        builder.Property(e => e.CreatedAt)
            .IsRequired()
            .HasDefaultValueSql("CURRENT_TIMESTAMP AT TIME ZONE 'UTC'");

        builder.Property(e => e.UpdatedAt)
            .IsRequired()
            .HasDefaultValueSql("CURRENT_TIMESTAMP AT TIME ZONE 'UTC'");

        // ═══════════════════════════════════════════════════════════════
        // INDEXES
        // ═══════════════════════════════════════════════════════════════
        builder.HasIndex(e => e.Name)
            .IsUnique();

        builder.HasIndex(e => e.OrganizationId);

        builder.HasIndex(e => new { e.OrganizationId, e.Name })
            .IsUnique();
    }
}

Template: Entity with Relationships

// src/{name}.infrastructure/Configurations/{Entity}Configuration.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using {name}.domain.{aggregate};

namespace {name}.infrastructure.configurations;

internal sealed class {Entity}Configuration : IEntityTypeConfiguration<{Entity}>
{
    public void Configure(EntityTypeBuilder<{Entity}> builder)
    {
        builder.ToTable("{entity}");
        builder.HasKey(e => e.Id);

        // ═══════════════════════════════════════════════════════════════
        // FOREIGN KEY PROPERTIES
        // ═══════════════════════════════════════════════════════════════
        builder.Property(e => e.OrganizationId)
            .IsRequired();

        builder.Property(e => e.ParentId);  // Nullable FK

        // ═══════════════════════════════════════════════════════════════
        // ONE-TO-MANY: Parent has many children
        // ═══════════════════════════════════════════════════════════════
        builder.HasMany(e => e.{ChildEntities})
            .WithOne(c => c.{Entity})
            .HasForeignKey(c => c.{Entity}Id)
            .OnDelete(DeleteBehavior.Cascade);

        // ═══════════════════════════════════════════════════════════════
        // MANY-TO-ONE: Entity belongs to Organization
        // ═══════════════════════════════════════════════════════════════
        builder.HasOne(e => e.Organization)
            .WithMany(o => o.{Entities})
            .HasForeignKey(e => e.OrganizationId)
            .OnDelete(DeleteBehavior.Restrict);  // Prevent cascade delete

        // ═══════════════════════════════════════════════════════════════
        // SELF-REFERENCING: Entity has optional parent
        // ═══════════════════════════════════════════════════════════════
        builder.HasOne(e => e.Parent)
            .WithMany(e => e.Children)
            .HasForeignKey(e => e.ParentId)
            .OnDelete(DeleteBehavior.Restrict)
            .IsRequired(false);
    }
}

Template: Child Entity Configuration

// src/{name}.infrastructure/Configurations/{ChildEntity}Configuration.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using {name}.domain.{aggregate};

namespace {name}.infrastructure.configurations;

internal sealed class {ChildEntity}Configuration : IEntityTypeConfiguration<{ChildEntity}>
{
    public void Configure(EntityTypeBuilder<{ChildEntity}> builder)
    {
        builder.ToTable("{child_entity}");
        
        builder.HasKey(c => c.Id);
        
        builder.Property(c => c.Id)
            .ValueGeneratedNever();

        builder.Property(c => c.{Parent}Id)
            .IsRequired();

        builder.Property(c => c.Name)
            .HasMaxLength(100)
            .IsRequired();

        builder.Property(c => c.SortOrder)
            .IsRequired()
            .HasDefaultValue(0);

        builder.Property(c => c.CreatedAt)
            .IsRequired()
            .HasDefaultValueSql("CURRENT_TIMESTAMP AT TIME ZONE 'UTC'");

        // Relationship defined from parent side, but can also define here
        builder.HasOne(c => c.{Parent})
            .WithMany(p => p.{ChildEntities})
            .HasForeignKey(c => c.{Parent}Id)
            .OnDelete(DeleteBehavior.Cascade);

        // Composite unique constraint
        builder.HasIndex(c => new { c.{Parent}Id, c.Name })
            .IsUnique();

        builder.HasIndex(c => new { c.{Parent}Id, c.SortOrder });
    }
}

Template: Many-to-Many Relationship

// src/{name}.infrastructure/Configurations/User{Entity}Configuration.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using {name}.domain.{aggregate};

namespace {name}.infrastructure.configurations;

// Join entity for many-to-many
internal sealed class User{Entity}Configuration : IEntityTypeConfiguration<User{Entity}>
{
    public void Configure(EntityTypeBuilder<User{Entity}> builder)
    {
        builder.ToTable("user_{entity}");

        // Composite primary key
        builder.HasKey(ue => new { ue.UserId, ue.{Entity}Id });

        // Or with separate ID
        // builder.HasKey(ue => ue.Id);
        // builder.HasIndex(ue => new { ue.UserId, ue.{Entity}Id }).IsUnique();

        builder.Property(ue => ue.UserId)
            .IsRequired();

        builder.Property(ue => ue.{Entity}Id)
            .IsRequired();

        builder.Property(ue => ue.IsManager)
            .HasDefaultValue(false);

        builder.Property(ue => ue.CreatedAt)
            .HasDefaultValueSql("CURRENT_TIMESTAMP AT TIME ZONE 'UTC'");

        // Relationships
        builder.HasOne(ue => ue.User)
            .WithMany(u => u.User{Entities})
            .HasForeignKey(ue => ue.UserId)
            .OnDelete(DeleteBehavior.Cascade);

        builder.HasOne(ue => ue.{Entity})
            .With