Question

I am trying to learn DDD, and i am making a simple demo project.

Right now, i have a generic repository

public class Repository<T> where T : class, IAggregateRoot
{
    public void Add(T entity)
    {
        ObjectSet.AddObject(entity);
    }
}

and a Product class

public class Product : IAggregateRoot
{
    private Guid _id = Guid.Empty;
    public Guid Id
    {
        get { return _id; }
        private set { _id = value; }
    }
    public string Name { get; private set; }

    protected Product() { }
    public Product(string name)
    {
        Name = name;
    }
}

The idea is that i want that a Product which has been created to have an empty Guid. It should get a new Guid only when is inserted into databse.

Product product = new Product("Hello World");
product.Id == Guid.Empty; // True

How is right now, when i call the repository to insert a product, it inserts it in database with an empty Guid.

var repository = new Repository<Product>();
repository.Add(product);

Where should i put the Guid generation of the Product? In the repository? If yes, how should i do it, because i have a generic repository.

Thank you

Answer 1

you can change the IAggregateRoot definition to add an ID property, like this

interface IAggregateRoot
{
    Guid Id { get; set;}
}

as every class of your project will have an id and will implement the IAggregateRoot interface, you can initialize the id inside the class constructor, like this:

public class Product : IAggregateRoot
{
    public Guid Id { get; set; }
    public string Name { get; private set; }


    protected Product() { }
    public Product(string name)
    {
        Id = Guid.Empty;
        Name = name;
    }
}

and inside the repository Add method, you can put the Guid.NewGuid(), and then pass it forward

public class Repository<T> where T : class, IAggregateRoot
{
    public void Add(T entity)
    {
        entity.Id = Guid.NewGuid();
        ObjectSet.AddObject(entity);
    }
}