DotNetBrightener.Mapper 2026.0.2

DotNetBrightener.Mapper

Copyright © 2017 - 2026 Vampire Coder (formerly DotnetBrightener)

DotNetBrightener.Mapper is a compile-time DTO and projection generator for .NET.

Define a target type once with MappingTarget<TSource>, and the generator produces the mapping surface for you:

• source constructor
• parameterless constructor when enabled
• Projection expression for LINQ and EF Core
• ToSource() for reverse mapping when enabled
• patch/update helpers through the mapping packages

The project is split into focused packages so you only install what you need.

Packages

Core generator

dotnet add package DotNetBrightener.Mapper

This package provides the source generator and analyzer support.

Attributes only

dotnet add package DotNetBrightener.Mapper.Attributes

Use this when you only need the runtime attributes and enums.

Mapping extensions

dotnet add package DotNetBrightener.Mapper.Mapping

This package adds:

• ToTarget
• ToSource
• SelectTargets
• SelectSources
• SelectTarget
• ApplyTarget
• ApplyTargetWithChanges
• custom mapping interfaces
• expression mapping helpers

EF Core mapping extensions

dotnet add package DotNetBrightener.Mapper.Mapping.EFCore

This package adds EF Core-specific helpers such as:

• ToTargetsAsync
• FirstAsync
• SingleAsync
• UpdateFromTarget
• UpdateFromTargetAsync
• UpdateFromTargetWithChanges

Quick Example

using DotNetBrightener.Mapper;

public class User
{
    public int Id { get; set; }
    public string FirstName { get; set; } = string.Empty;
    public string LastName { get; set; } = string.Empty;
    public string Email { get; set; } = string.Empty;
    public string Password { get; set; } = string.Empty;
    public DateTime CreatedAt { get; set; }
}

[MappingTarget<User>("Password", "CreatedAt", GenerateToSource = true)]
public partial class UserDto;

The generated UserDto includes the mapped properties from User, a constructor from User, a Projection expression, and ToSource() because GenerateToSource = true.

Basic Mapping

With DotNetBrightener.Mapper.Mapping installed:

using DotNetBrightener.Mapper.Mapping;

var dto = user.ToTarget<UserDto>();
var dtoFast = user.ToTarget<User, UserDto>();

var entity = dto.ToSource<User>();
var entityFast = dto.ToSource<UserDto, User>();

var dtos = users.SelectTargets<UserDto>().ToList();
var projected = query.SelectTarget<UserDto>();

Nested Target Types

public class Address
{
    public string Street { get; set; } = string.Empty;
    public string City { get; set; } = string.Empty;
}

public class Company
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public Address HeadquartersAddress { get; set; } = null!;
}

[MappingTarget<Address>]
public partial record AddressDto;

[MappingTarget<Company>(NestedTargetTypes = [typeof(AddressDto)])]
public partial record CompanyDto;

Nested object and collection mappings are generated automatically when the nested target types are declared.

Custom Mapping

Static mapper:

using DotNetBrightener.Mapper.Mapping;
using DotNetBrightener.Mapper.Mapping.Configurations;

public class UserMapper : IMappingConfiguration<User, UserDto>
{
    public static void Map(User source, UserDto target)
    {
        target.FullName = $"{source.FirstName} {source.LastName}";
    }
}

[MappingTarget<User>(Configuration = typeof(UserMapper))]
public partial class UserDto
{
    public string FullName { get; set; } = string.Empty;
}

Instance mapper with DI:

using DotNetBrightener.Mapper.Mapping.Configurations;

public class UserMapperWithServices : IMappingConfigurationAsyncInstance<User, UserDto>
{
    private readonly IProfileService _profileService;

    public UserMapperWithServices(IProfileService profileService)
    {
        _profileService = profileService;
    }

    public async Task MapAsync(User source, UserDto target, CancellationToken cancellationToken = default)
    {
        target.ProfileUrl = await _profileService.GetProfileUrlAsync(source.Id, cancellationToken);
    }
}

Additional Attributes

The generator also supports:

• MapFrom
• MapWhen
• Flatten
• GenerateDtos
• Wrapper

Additional generation options include:

• Include
• CopyAttributes
• NullableProperties
• ConvertEnumsTo
• GenerateEquality
• GenerateCopyConstructor
• SourceSignature

Documentation

• Overview
• Quick start
• MappingTarget attribute reference
• Extension methods
• Advanced scenarios
• Generated code examples
• Async mapping
• GenerateDtos
• Expression mapping
• Flatten
• Wrapper
• MapFrom
• Source signature tracking
• MapWhen
• Inheritance mapping
• Mapping hooks
• Enum conversion

Project Packages

• DotNetBrightener.Mapper
• DotNetBrightener.Mapper.Attributes
• DotNetBrightener.Mapper.Mapping
• DotNetBrightener.Mapper.Mapping.EFCore
• DotNetBrightener.Mapper.Dashboard