FlowMapper 1.0.0

FlowMapper

Compile-time object mapping for .NET — powered by Roslyn Source Generators.

FlowMapper generates pure C# mapping code at build time. Zero reflection, zero expression trees, zero runtime overhead.

Install

dotnet add package FlowMapper

This meta-package includes Abstractions, Core, SourceGenerator, Analyzers, and DependencyInjection.

How it works

Define a MappingProfile class and configure mappings with the fluent API. FlowMapper generates the implementation at compile time.

Fluent API

The fluent API is the heart of FlowMapper. Every method returns MappingExpression<TSource, TDestination> for chaining.

using FlowMapper;

public class MyProfile : MappingProfile
{
    public MyProfile()
    {
        CreateMap<User, UserDto>()
            .ForMember(dest => dest.FullName, opt => opt.MapFrom(src => $"{src.FirstName} {src.LastName}"))
            .ForMember(dest => dest.Age, opt => opt.MapFrom(src => src.Age))
            .Ignore(dest => dest.InternalId)
            .UseConstructor()
            .DisableFlatten()
            .AfterMap((source, target) => target.CreatedAt = DateTime.UtcNow)
            .ConstructUsing(source => new UserDto { Id = source.Id });
    }
}

ForMember options

CreateMap<Order, OrderDto>()
    .ForMember(dest => dest.Total, opt => opt.MapFrom(src => src.Items.Sum(i => i.Price)))
    .ForMember(dest => dest.ShippingAddress, opt => opt.Ignore());

Examples

Basic mapping

var user = new User { Id = 1, Name = "Alice", Email = "alice@example.com" };
var dto = new UserMapper().Map(user);

Console.WriteLine(dto.Name); // Alice

Nested & flatten mapping

CreateMap<Order, OrderDto>();

var order = new Order
{
    Id = 42,
    Customer = new Customer
    {
        Name = "Bob",
        Address = new Address { Street = "123 Main St", City = "Springfield" }
    }
};

var dto = new OrderMapper().Map(order);
Console.WriteLine($"{dto.CustomerName} — {dto.Street}, {dto.City}");
// Bob — 123 Main St, Springfield

Constructor mapping (records)

public record ProductDto(int Id, string Name, decimal Price);

CreateMap<Product, ProductDto>().UseConstructor();

var product = new Product { Id = 1, Name = "Widget", Price = 9.99m };
var dto = new ProductMapper().Map(product);

Dependency Injection

builder.Services.AddFlowMapper();

public class MyService(IMapper<User, UserDto> mapper)
{
    public UserDto GetUser(int id) => mapper.Map(_repository.Get(id));
}

Performance

FlowMapper matches hand-written mapping speed — 6–10× faster than AutoMapper with identical memory allocation.

BenchmarkDotNet results on .NET 10 (mean time per operation, lower is better):

Run the benchmark yourself: dotnet run -c Release --project samples/Benchmark

Diagnostics at compile time

Mapping issues are reported as build warnings and errors — no more runtime surprises.

Requirements

• .NET 6+ or .NET Standard 2.0+
• C# 12+

License

MIT