Drag ‘n’ dropping items has its various popular uses and shopping carts are definitely one of them.
In this tutorial, we’ll be creating a simple shopping cart that works with drag ‘n’ drops.
It will have support for add-to-basket with quantity updates (so that the same items could be added more than once) and removing items from the basket.

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A common requirement is to have applications share data with other programs. Although there are interfaces available to work with, for example, Microsoft Excel data files, this approach is generally complex, involves a fair amount of overhead, and requires that support libraries accompany your application

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In this version:

public class Entity<T>
{

  public T Id { get; protected set; }

}

In summary, the most important issues here are:

• The Aggregate’s main task is to protect invariants (business rules, the boundary of immediate consistency)
• In a multi-threaded environment, when multiple threads are running simultaneously on the same Aggregate, a business rule may be broken
• A way to solve concurrency conflicts is to use Pessimistic or Optimistic concurrency techniques
• Pessimistic Concurrency involves the use of a database transaction and a locking mechanism. In this way, requests are processed one after the other, so basically concurrency is lost and it can lead to deadlocks.
• Optimistic Concurrency technique is based on versioning database records and checking whether the previously loaded version has not been changed by another thread.
• Entity Framework Core supports Optimistic Concurrency. Pessimistic Concurrency is not supported
• The Aggregate must always be treated and versioned as a single unit
• Domain events are an indicator, that state was changed so Aggregate version should be changed as well 

public class AggregateRootBase : Entity, IAggregateRoot
{
    private int _versionId;

    public void IncreaseVersion()
    {
        _versionId++;
    }
}

internal sealed class OrderEntityTypeConfiguration : IEntityTypeConfiguration<Order>
{
    public void Configure(EntityTypeBuilder<Order> builder)
    {
        builder.Property("_versionId").HasColumnName("VersionId").IsConcurrencyToken();
 
        //...
    }
}

var order = await _ordersContext.Orders.FindAsync(orderId);
order.AddOrderLine(request.ProductCode); 
var domainEvents = DomainEventsHelper.GetAllDomainEvents(order);
if (domainEvents.Any())
{
    order.IncreaseVersion();
}
await _ordersContext.SaveChangesAsync();