DeltaMapper.OpenTelemetry 0.1.0-alpha

<p align="center"> <img src="icon.png" alt="DeltaMapper" width="200" /> <br /> <h1 align="center">DeltaMapper</h1> <p align="center"><em>Fast, diff-aware .NET object mapper. MIT licensed. Minimal dependencies.</em></p> <p align="center"> <a href="https://www.nuget.org/packages/DeltaMapper"><img src="https://img.shields.io/nuget/v/DeltaMapper.svg" alt="NuGet" /></a> <a href="https://github.com/OrodruinLabs/DeltaMapper/actions/workflows/ci.yml"><img src="https://github.com/OrodruinLabs/DeltaMapper/actions/workflows/ci.yml/badge.svg" alt="Build" /></a> <a href="LICENSE"><img src="https://img.shields.io/badge/License-MIT-blue.svg" alt="License: MIT" /></a> </p> </p>

Why DeltaMapper?

• Near-zero overhead — source-generated direct calls run at 7 ns, same as hand-written code
• MappingDiff<T> — map and get a structured change set in one call
• Source generator — [GenerateMap] emits assignment code at build time, zero reflection
• Full IMapper pipeline — DI, middleware, hooks, EF Core proxy detection, OpenTelemetry tracing

Install

dotnet add package DeltaMapper                    # core runtime
dotnet add package DeltaMapper.SourceGen          # optional: compile-time codegen
dotnet add package DeltaMapper.EFCore             # optional: EF Core proxy awareness
dotnet add package DeltaMapper.OpenTelemetry      # optional: Activity spans

Requires .NET 10+.

Quick Start

// 1. Define a profile
public class UserProfile : MappingProfile
{
    public UserProfile()
    {
        CreateMap<User, UserDto>()
            .ForMember(d => d.FullName, o => o.MapFrom(s => $"{s.First} {s.Last}"))
            .ReverseMap();
    }
}

// 2. Build & map
var mapper = MapperConfiguration.Create(cfg => cfg.AddProfile<UserProfile>())
    .CreateMapper();

var dto = mapper.Map<User, UserDto>(user);

Built-in Change Tracking

var diff = mapper.Patch(updateDto, existingUser);

if (diff.HasChanges)
    await auditLog.RecordAsync(userId, diff.Changes);

diff.Changes is IReadOnlyList<PropertyChange> — each entry has PropertyName, From, To, ChangeKind. Nested paths use dot-notation ("Address.City").

Performance

DeltaMapper's source generator produces code as fast as hand-written — and on collections, faster than every competitor tested.

.NET 10. Times are per single mapping operation. DeltaMapper allocates only the destination object — no framework overhead.

Full benchmark results and methodology

Documentation

What's Included

• Runtime core — profiles, convention matching, DI integration
• MappingDiff<T> — structured change sets with Patch()
• Roslyn source generator with zero-overhead direct call methods
• EF Core proxy detection middleware
• OpenTelemetry tracing middleware
• BenchmarkDotNet suite comparing against Mapperly, AutoMapper, and hand-written code

License

MIT. See LICENSE.