Dknet Domain Entity

Project Conventions (from actual codebase)

Inheritance Hierarchy

AuditedEntity<Guid>        ← from DKNet.EfCore.Abstractions.Entities
  └── DomainEntity          ← Minimal.Domains.Share (abstract, Guid Id + audit)
       └── AggregateRoot    ← Minimal.Domains.Share (abstract, Guid auto-gen)

Key Rules

• Entities are NOT sealed — they inherit from AggregateRoot (or DomainEntity for non-root entities)
• Properties use { get; private set; } — mutation happens ONLY through named methods
• Constructor sets immutable fields; Update(...) method handles mutable fields
• SetCreatedBy(userId) and SetUpdatedBy(userId) are inherited from AuditedEntity
• Entity uses AddEvent(...) to publish domain events (inherited from base)
• Guid.Empty for Id means "let the database generate it"

File Location

src/ApiEndpoints/Minimal.Domains/
├── Features/
│   └── {Feature}/
│       └── Entities/
│           ├── {Entity}.cs              ← Aggregate root
│           ├── {OwnedType}.cs           ← Owned value objects (optional)
│           └── {ChildEntity}.cs         ← Non-root entities (optional)
├── Services/
│   ├── I{Service}.cs                    ← Domain service interfaces
│   └── IDomainService.cs               ← Marker interface
└── Share/
    ├── AggregateRoot.cs                 ← DO NOT MODIFY
    ├── DomainEntity.cs                  ← DO NOT MODIFY
    ├── DomainSchemas.cs                 ← ADD your schema constant here
    └── Sequences.cs                     ← ADD sequence name if needed

Step-by-Step

Step 1: Add Schema Constant

Edit src/ApiEndpoints/Minimal.Domains/Share/DomainSchemas.cs:

public static class DomainSchemas
{
    public const string Migration = "migrate";
    public const string Profile = "pro";
    public const string {Feature} = "{prefix}";    // ← ADD THIS
}

Step 2: Create the Entity Class

Create src/ApiEndpoints/Minimal.Domains/Features/{Feature}/Entities/{Entity}.cs:

using Minimal.Domains.Share;

namespace Minimal.Domains.Features.{Feature}.Entities;

/// <summary>
/// {Description of the aggregate root}.
/// </summary>
public class {Entity} : AggregateRoot
{
    #region Constructors

    /// <summary>
    /// Creates a new {Entity} with a system-assigned identity.
    /// </summary>
    public {Entity}(
        {constructor params for immutable + mutable fields},
        string byUser)
        : this(Guid.Empty, {forward all params}, byUser)
    {
    }

    /// <summary>
    /// Rehydrates an existing {Entity} from persistence.
    /// </summary>
    internal {Entity}(
        Guid id,
        {all params},
        string createdBy)
        : base(id, createdBy)
    {
        // Set immutable properties
        {ImmutableProp} = {value};

        // Delegate mutable fields to Update
        Update({mutable params}, createdBy);
    }

    #endregion

    #region Properties

    // Immutable properties (set only in constructor)
    public string {ImmutableProp} { get; private set; }

    // Mutable properties (changed via Update method)
    public string? {MutableProp} { get; private set; }

    #endregion

    #region Methods

    /// <summary>
    /// Updates mutable fields. Null/empty values are ignored (preserves current).
    /// </summary>
    public void Update({mutable params}, string userId)
    {
        if (!string.IsNullOrEmpty({param}))
        {
            {MutableProp} = {param};
        }

        SetUpdatedBy(userId);
    }

    #endregion
}

Step 3: Create Owned Value Objects (if needed)

For complex nested types that don't have their own identity:

namespace Minimal.Domains.Features.{Feature}.Entities;

/// <summary>
/// {Description} — owned value object, no independent identity.
/// </summary>
public class {OwnedType}
{
    public string {Prop1} { get; set; } = default!;
    public string? {Prop2} { get; set; }
}

Step 4: Create Domain Service Interface (if needed)

If the entity needs external ID generation or cross-aggregate lookups:

namespace Minimal.Domains.Services;

public interface I{Service} : IDomainService
{
    Task<string> NextValueAsync();
}

Step 5: Add Sequence (if using auto-generated IDs)

Edit src/ApiEndpoints/Minimal.Domains/Share/Sequences.cs to add sequence name:

public static class Sequences
{
    public const string {Entity}Seq = "{entity}_seq";
}

Reference: CustomerProfile (actual production code)

public class CustomerProfile : AggregateRoot
{
    // Constructor: new entity
    public CustomerProfile(string name, string membershipNo, string email, string phone, string byUser)
        : this(Guid.Empty, name, membershipNo, email, phone, byUser) { }

    // Constructor: rehydration
    internal CustomerProfile(Guid id, string name, string membershipNo, string email, string phone, string createdBy)
        : base(id, createdBy)
    {
        Name = name;
        Email = email;
        MembershipNo = membershipNo;
        Update(null, name, phone, null, createdBy);
    }

    // Immutable
    public string Email { get; private set; }
    public string MembershipNo { get; private set; }

    // Mutable
    public string Name { get; private set; }
    public string? Phone { get; private set; }
    public string? Avatar { get; private set; }
    public DateTime? BirthDay { get; private set; }

    public void Update(string? avatar, string? name, string? phoneNumber, DateTime? birthday, string userId)
    {
        Avatar = avatar;
        BirthDay = birthday;
        if (!string.IsNullOrEmpty(name)) Name = name;
        if (!string.IsNullOrEmpty(phoneNumber)) Phone = phoneNumber;
        SetUpdatedBy(userId);
    }
}

Validation Checklist

• Entity inherits from AggregateRoot (not sealed, not using required keyword)
• Properties use { get; private set; } — no public setters
• Constructor takes string byUser as last param; passes to base(id, createdBy)
• Public constructor uses Guid.Empty for new entities
• Internal constructor used for rehydration from persistence
• Update(...) method calls SetUpdatedBy(userId) at the end
• Immutable fields set only in constructor
• Schema constant added to DomainSchemas.cs
• Namespace follows Minimal.Domains.Features.{Feature}.Entities
• File placed in src/ApiEndpoints/Minimal.Domains/Features/{Feature}/Entities/
• Domain service interface extends IDomainService (if applicable)
• XML doc comments on class and all public members
• dotnet build src/DKNet.Templates.sln -c Release passes with zero warnings

Common Mistakes

Next Steps

After creating the domain entity, proceed to: → dknet-efcore-config skill to create the EF Core mapper configuration