Defining the domain layer abstraction

Once the PackagesManagementDomain Standard 2.1 library project has been added to the solution, we’ll add a Tools folder to the project root. Then, we’ll place all the DomainLayer tools contained in the code associated with ch11. Since the code contained in this folder uses data annotations and defines DI extension methods, we must also add references to the System.ComponentModel.Annotations and Microsoft.Extensions.DependencyInjection.Abstration NuGet packages.

Then, we need an Aggregates folder containing all the aggregate definitions (remember, we implemented aggregates as interfaces), namely, IDestination, IPackage, and IPackageEvent. Here, IPackageEvent is the aggregate associated with the table where we will place events to be propagated to other applications.

As an example, let’s analyze IPackage:

public interface IPackage : IEntity<int>
{
    void FullUpdate(IPackageFullEditDTO packageDTO);
    string...