Quick start

1. Install

dotnet add package Valiant.Mapping

Valiant.Mapping contains the runtime API and delivers its source generator as an analyzer. No separate generator package is needed.

2. Declare the models and mapper

using Valiant.Mapping;

public sealed class User
{
    public required string Name { get; init; }
    public int Age { get; init; }
}

public sealed record UserDto(string Name, int Age);

[ValiantMapper]
public sealed partial class UserMapper : MapperDefinition<User, UserDto>;

The mapper must be partial. MapperDefinition<TSource, TTarget> identifies the pair and the generator fills in the implementation.

3. Map

var mapper = new UserMapper();
var dto = mapper.Map(new User { Name = "Ada", Age = 36 });

The mapper can also be consumed through its interface:

IMapper<User, UserDto> mapper = new UserMapper();
UserDto dto = mapper.Map(user);

4. Register with dependency injection

When the project references Microsoft dependency-injection abstractions, Valiant generates AddValiantMappers:

using Valiant.Mapping.DependencyInjection;

builder.Services.AddValiantMappers(options =>
{
    options.Mode = ValiantMappingMode.Auto;
    options.NullHandling = ValiantNullHandling.MapNulls;
});

Then inject the concrete mapper, IMapper<User, UserDto>, the non-generic IMapper, or IMapperFactory.

Generated discovery

Only declarations marked with [ValiantMapper] enter the generator pipeline. Valiant does not scan every type in your compilation looking for mapping definitions.

Next: learn what maps automatically in Convention mapping.