I'm currently trying to define certain base classes & interfaces to use them in DDD & CQRS projects, however I'm struggling with the definition of aggregates and aggregate roots.

The blue book tells us that...

• An aggregate is a cluster of objects
• Each aggregate has a aggregate root
• The aggregate root is a specific entity and the only object other parts of the application can reference to.

For this, I made the following classes / interfaces:

Entity

public interface IEntity {

    TKey Key { get; set; }

}

public abstract class EntityBase : IEntity {

    // key stuff, equality comparer..

}

Aggregate Root

public interface IAggregateRoot : IEntity
{
}

Repository

public interface IRepository
    where TAggregate : IAggregate
    where TRoot : IAggregateRoot
{

    TRoot Root { get; set; }

    void Add(TAggregate aggregate);

}

Now, did I understood this correctly? How might a aggregate interface look like then?

public interface IAggregate
    where TRoot : IAggregateRoot
{

}

I tried to find some references and in a CQRS framework I found the following implementation: (Does CQRS differ so much from DDD? I thought it's pretty much the same when not applying event sourcing)

public abstract class Entity where TAggregateRoot
    : AggregateRoot
{

}