Defining the domain layer interface

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 ch7. 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 (which, as already said, we will implement as interfaces).

Below is an example of an aggregate definition:

public interface IPackage : IEntity<int>
{
    void FullUpdate(IPackageFullEditDTO packageDTO);
    string Name { get; set; }
    string Description { get;}
    decimal Price { get; set; }
    int DurationInDays { get; }
    DateTime? StartValidityDate { get;}
    DateTime? EndValidityDate...