Value object

In Domain-Driven Design, a value object is a concept used to model a descriptive aspect of the domain with no conceptual identity. In contrast to entities, which are defined by their identity, value objects are defined by their attributes. Essentially, a value object is a small, immutable object that represents a descriptive aspect of the domain.

Packages

Package	Link	Application in section
LeanCode.DomainModels		IAggregateRoot, ValueObject
LeanCode.DomainModels.Generators		Ids

Example

Let's add an address to Employee aggregate defined in aggregate section.

public class Employee : IAggregateRoot<EmployeeId>
{
    // . . .
    public Address? Address { get; private set; }
    // . . .

    public void SetAddress(Address address)
    {
        Address = address;
    }
}

public record Address(string Street, string City) : ValueObject
{
    public string Street { get; private init; } = Street;
    public string City { get; private init; } = City;
}

Notice that Address class is defined as a record in C#. Records are a concise way to create immutable objects, making them suitable for value objects. Address is a value object as it's defined only by its properties, meaning that two addresses with same properties are treated as the same address.

How to use records as value objects

• All properties must have private init setters.
• Always remember that C# uses default value comparator (in case of arrays and collections this is reference equality).