TaskHub.Shared

Using Value Objects

Value Objects are objects that describe descriptive aspects of the domain with no conceptual identity. In TaskHub.Shared, they are used to wrap primitive types and enforce validation.

Benefits of Value Objects

• Type Safety: Distinguish between an Email and a string.
• Validation: An Email object can only be created if it contains a valid email address.
• Business Logic: Methods related to the data (e.g., Email.GetDomain()) live with the data.

Built-in Value Objects

The TaskHub.Shared.ValueObjects module includes many common types:

• Email, PhoneNumber, FirstName, LastName, FullName.
• UserId, ClientId, JobId (Guid wrappers).
• LatLng (Coordinates).
• Title, Text, Comment.

Usage Example

public record User(UserId Id, Email Email, FullName Name) : AggregateBase<UserId>(Id);

// Usage in a Command
public record RegisterUserCommand(string Email, string FirstName, string LastName) : ICommand;

// Usage in a Handler
public async Task<Result> HandleAsync(RegisterUserCommand cmd, CancellationToken ct)
{
    // Validation happens during instantiation
    var email = new Email(cmd.Email); 
    var name = new FullName(cmd.FirstName, cmd.LastName);
    
    var user = new User(UserId.New(), email, name);
    // ...
}

JSON & EF Core Support

TaskHub.Shared provides converters to ensure Value Objects are correctly handled by:

• System.Text.Json: Automatically serialized/deserialized to their primitive values.
• EF Core: Automatically mapped to database columns using Value Converters.

EF Core Configuration Example

builder.Property(x => x.Email)
    .HasConversion(x => x.Value, x => new Email(x))
    .HasMaxLength(256);

Creating Your Own

If you need a custom value object, follow this pattern:

public record MyValueObject
{
    public string Value { get; init; }

    public MyValueObject(string value)
    {
        if (string.IsNullOrWhiteSpace(value)) throw new ValueObjectException("Cannot be empty");
        Value = value;
    }

    public static implicit operator string(MyValueObject obj) => obj.Value;
}

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