This is a new project, any help, feedback and contributions are highy appreciated.
"One part of a subject, situation, etc. that has many parts."
Facet is a compile-time source generator that creates partial classes from existing types — by copying only the members you want.
Exclude properties, include public fields, add your own members, or generate a constructor — all with a single [Facet] attribute.
Use Facet to build lightweight DTOs, API shapes, or UI-bound view models without writing boilerplate or mapping code.
dotnet add package FacetDefine a partial class, attach the Facet attribute and you're done.
using Facet;
public class Person
{
public string Name { get; set; }
public string Email { get; set; }
public int Age { get; set; }
public Guid RawId;
}
// Generate class that can be mapped from source model
[Facet(typeof(Person), GenerateConstructor = true)]
public partial class PersonDto { }
// Generate class while adding and removing properties
// You can pass an array of properties to exclude
[Facet(typeof(Person), exclude: nameof(Person.Email)]
public partial class PersonWithNote
{
public string Note { get; set; }
}The PersonDto will have a constructor that maps the source type properties.
PersonWithNote is generated and will not have the Email property, but will have the Note property.
var person = new Person
{
Name = "Tim",
Email = "hidden@example.com",
Age = 33,
RawId = Guid.NewGuid()
};
var dto = new PersonDto(person);If you want to map properties with custom logic, you can use the Facet.Mapping package.
dotnet add package Facet.MappingSource model:
public class User
{
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime Registered { get; set; }
}Target facet:
[Facet(
typeof(User),
exclude: new[] { nameof(User.FirstName), nameof(User.LastName), nameof(User.Registered) },
Configuration = typeof(UserMapper))]
public partial class UserDto
{
public string FullName { get; set; }
public string RegisteredText { get; set; }
}Mapping configuration from source to your facet:
public class UserMapper : IFacetMapConfiguration<User, UserDto>
{
public static void Map(User source, UserDto target)
{
target.FullName = $"{source.FirstName} {source.LastName}";
target.RegisteredText = source.Registered.ToString("yyyy-MM-dd");
}
}var user = new User
{
FirstName = "Tim",
LastName = "Maes",
Registered = new DateTime(2020, 1, 15)
}
var dto = new UserDto(user);
Console.WriteLine(dto.FullName); // Tim Maes
Console.WriteLine(dto.RegisteredText); // 2020-01-15