This is a new project, any help, feedback and contributions are highy appreciated.
"One part of a subject, situation, object that has many parts."
Facet is a C# source generator that produces slim DTOs, typed projections, and API-bound view models — directly from your domain models.
Zero runtime cost, no boilerplate.
- ✳️ Generate partial classes or records based on existing types
- 🔧 Exclude fields/properties you don’t need, or add new ones
- 📫 Include public fields (opt-in)
- 🔨 Support custom mapping logic
- 🔗 Auto-generate constructors to initialize target from source
- 🔩 Works with records, classes, readonly, and init-only members
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; }
}
[Facet(typeof(Person), Kind = FacetKind.Record]
public partial record PersonRecord
{
// ..
}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.
PersoneRecord is generated as a record
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[] { ... }, //optional
Configuration = typeof(UserMapConfig))]
public partial class UserDto
{
public string FullName { get; set; }
public string RegisteredText { get; set; }
}Mapping configuration from source to your facet:
public class UserMappConfig : 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");
}
}Now you can just create a DTO instance, and the source object will be mapped accordingly.
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