Simple.AutoMapper

High-performance object mapping for .NET with expression tree compilation. Simple API, powerful configuration options.

v1.0.9 - Added Condition, NullSubstitute, BeforeMap/AfterMap, ConstructUsing. See Release Notes.

Installation

dotnet add package Simple.AutoMapper

Target Frameworks: netstandard2.0, netstandard2.1, net8.0, net9.0, net10.0

Quick Start

using Simple.AutoMapper.Core;

// Simple mapping - no configuration needed
var dto = Mapper.Map<User, UserDto>(user);
var dtos = Mapper.Map<User, UserDto>(users);

// In-place update
Mapper.Map(source, existingDestination);

Configuration Options

Basic Configuration

// Configure mapping with options
Mapper.CreateMap<User, UserDto>()
    .Ignore(d => d.Password)
    .ReverseMap();  // Creates UserDto -> User mapping too

ForMember with MapFrom

Mapper.CreateMap<User, UserDto>()
    .ForMember(d => d.FullName, opt => opt.MapFrom(s => $"{s.FirstName} {s.LastName}"))
    .ForMember(d => d.Age, opt => opt.MapFrom(s => DateTime.Now.Year - s.BirthYear));

Condition - Conditional Mapping

Mapper.CreateMap<User, UserDto>()
    .ForMember(d => d.Email, opt => {
        opt.MapFrom(s => s.Email);
        opt.Condition(s => s.IsEmailVerified);  // Only map if condition is true
    });

NullSubstitute - Default Values

Mapper.CreateMap<User, UserDto>()
    .ForMember(d => d.DisplayName, opt => {
        opt.MapFrom(s => s.Nickname);
        opt.NullSubstitute("Anonymous");  // Use "Anonymous" if source is null
    });

BeforeMap / AfterMap - Callbacks

Mapper.CreateMap<User, UserDto>()
    .BeforeMap((src, dest) => {
        // Execute before property mapping
        dest.MappedAt = DateTime.UtcNow;
    })
    .AfterMap((src, dest) => {
        // Execute after property mapping
        dest.FullName = $"{dest.FirstName} {dest.LastName}";
    });

ConstructUsing - Custom Construction

// For types without parameterless constructor
Mapper.CreateMap<User, UserDto>()
    .ConstructUsing(src => new UserDto(src.Id));

// For immutable objects
Mapper.CreateMap<User, ImmutableUserDto>()
    .ConstructUsing(src => new ImmutableUserDto(
        src.Id,
        src.Name,
        src.Email
    ));

Circular Reference Handling

Mapper.CreateMap<Parent, ParentDto>()
    .PreserveReferences()  // Handle circular references
    .MaxDepth(5);          // Limit recursion depth

Dependency Injection

// In Program.cs or Startup.cs
services.AddSimpleMapper(cfg => {
    cfg.AddProfile<UserMappingProfile>();
});

// Or scan assemblies
services.AddSimpleMapper(typeof(UserMappingProfile).Assembly);

Creating Profiles

public class UserMappingProfile : Profile
{
    public UserMappingProfile()
    {
        CreateMap<User, UserDto>()
            .ForMember(d => d.FullName, opt => opt.MapFrom(s => $"{s.FirstName} {s.LastName}"));

        CreateMap<Address, AddressDto>();
    }
}

EF Core Integration

Read Operations

// Materialize first, then map
var users = await db.Users
    .AsNoTracking()
    .Include(u => u.Address)
    .ToListAsync();

var dtos = Mapper.Map<User, UserDto>(users);

Write Operations

// Create
var entity = Mapper.Map<CreateUserDto, User>(dto);
await db.Users.AddAsync(entity);

// Update in-place
var entity = await db.Users.FindAsync(id);
Mapper.Map(dto, entity);
await db.SaveChangesAsync();

Collection Sync

var result = Mapper.Map(
    dtoList,
    entityList,
    dto => dto.Id,
    entity => entity.Id,
    removeMissing: true
);
// result.Added, result.Updated, result.Removed

Type Support

Type	Support
Simple types (int, string, DateTime, Guid, etc.)	✅
Nullable types	✅
Enums	✅
Complex types (classes)	✅ Recursive
Collections (List, Array, IEnumerable)	✅
Circular references	✅ With PreserveReferences()

Performance

• Expression tree compilation for fast subsequent mappings
• Thread-safe caching of compiled mappers
• First mapping incurs compilation cost; subsequent calls are optimized

Samples & Tests

• See samples/ for end-to-end usage examples
• See tests/ for comprehensive test coverage including edge cases

License

MIT License - see LICENSE.md

Team

Core Development Team

• SEONGAHN - Lead Developer & Project Architect
• YUJIN - Senior Developer & Exchange Integration Specialist
• SEJIN - Software Developer & API Implementation

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Built with care by the ODINSOFT Team | GitHub