ConventionMapper.SourceGenerator 1.2.0

ConventionMapper.SourceGenerator

Build-time object mapping. You declare partial mapping methods; the generator writes the implementation into your project when it compiles.

• No reflection at runtime. The output is plain C# assignments, loops and constructor calls.
• Native AOT and trimming safe. The package has no runtime dependency, not even on ConventionMapper.
• As fast as hand-written code. There is no configuration lookup, no boxing, no delegate per member.
• Debuggable. Step into the generated method like any other code (in Visual Studio: Go To Definition on the method, or look under Dependencies → Analyzers → ConventionMapper.SourceGenerator).
• Mistakes are build errors. An unmapped destination member fails the build (CM0001) instead of showing up at runtime.

dotnet add package ConventionMapper.SourceGenerator

Requires the .NET 8 SDK or later (Visual Studio 2022 17.8+) and C# 9 or later. The generated code itself runs on every target framework, including .NET Framework and netstandard2.0.

Declaring a mapper

using ConventionMapper;

[GeneratedMapper]
public static partial class OrderMapper
{
    // TDestination Map(TSource): creates a new object
    public static partial OrderDto ToDto(this Order order);

    // void Map(TSource, TTarget): updates an existing object
    public static partial void Update(OrderDto source, Order target);

    // collections, enums and other types work at the root too
    public static partial List<OrderLineDto> ToDtos(IEnumerable<OrderLine> lines);
}

OrderDto dto = order.ToDto();

Mappers can be static or instance classes, nested inside other partial types, and methods can be extension methods. The attributes are added to your project by the generator and are removed from the compiled assembly.

What gets mapped

Values of the same type are assigned as they are (reference types are not cloned).

Configuring members

[MapMember("Customer.Email", "ContactEmail")]   // source path -> destination member (or constructor parameter)
[MapIgnore("InternalNotes")]                    // leave a destination member out
public static partial OrderDto ToDto(Order order);

Diagnostics

Severities can be changed in .editorconfig, for example dotnet_diagnostic.CM0003.severity = warning.

Source generator or runtime mapper?

Use the generator for hot paths, Native AOT, trimming and when you want compile-time guarantees. Use the runtime ConventionMapper package for ProjectTo (LINQ / EF Core), DI-resolved resolvers and converters, Patch, collection merging by key and other configuration-driven features. Both packages can be used in the same project.