Events

An event is something significant that has happened in the domain. It encapsulates all relevant data of the action that happened.

{% hint style="success" %} You can/should/must...

• an event must be immutable
• an event must represent a domain event that already happened with a name in the past tense
• an event can be dispatched only by one aggregate {% endhint %}

To create an event with Cronus, just use the IEvent markup interface.

// TODO: give a relevant example
[DataContract(Name = "d2b92ca6-34bc-4670-890e-8dff6de624b6")]
public class ExampleCreated : IEvent
{
    public ExampleCreated(ExampleId id, ExampleName name)
    {
        if (id is null) throw new ArgumentNullException(nameof(id));
        if (name is null) throw new ArgumentNullException(nameof(name));

        Id = id;
        Name = name;
    }

    [DataMember(Order = 1)]
    public ExampleId Id { get; private set; }

    [DataMember(Order = 2)]
    public ExampleName Name { get; private set; }

    public override string ToString()
    {
        return $"Example with id '{Id}' and name '{Name}' has been created";
    }
}

{% hint style="info" %} Cronus uses the ToString() method for logging, so you can override it to generate user-readable logs. Otherwise, the name of the event class will be used for log messages. {% endhint %}