Migration from FunctionalDDD

Time: 15-30 min | Prerequisites: Existing project using FunctionalDdd.* packages

This guide covers migrating from the FunctionalDdd.* NuGet packages to the renamed Trellis.* packages. No API changes — all types, methods, and behaviors remain identical.

Package Mapping

Old Package	New Package
`FunctionalDdd.RailwayOrientedProgramming`	`Trellis.Results`
`FunctionalDdd.DomainDrivenDesign`	`Trellis.DomainDrivenDesign`
`FunctionalDdd.PrimitiveValueObjects`	`Trellis.Primitives`
`FunctionalDdd.PrimitiveValueObjectGenerator`	`Trellis.Primitives.Generator`
`FunctionalDdd.Asp`	`Trellis.Asp`
`FunctionalDdd.Http`	`Trellis.Http`
`FunctionalDdd.FluentValidation`	`Trellis.FluentValidation`
`FunctionalDdd.ArdalisSpecification`	Removed (replaced by native `Specification<T>` in `Trellis.DomainDrivenDesign`)

New packages with no previous equivalent:

Package	Purpose
`Trellis.Analyzers`	19 Roslyn analyzers enforcing ROP best practices
`Trellis.Testing`	FluentAssertions extensions, test builders, fakes
`Trellis.Stateless`	Wraps Stateless state machine Fire() to return Result<T>

Step-by-Step Migration

1. Update Package References

If you use Directory.Packages.props (recommended), update it in one place:

<!-- Before -->
<PackageVersion Include="FunctionalDdd.RailwayOrientedProgramming" Version="2.x.x" />
<PackageVersion Include="FunctionalDdd.DomainDrivenDesign" Version="2.x.x" />
<PackageVersion Include="FunctionalDdd.Asp" Version="2.x.x" />
<PackageVersion Include="FunctionalDdd.PrimitiveValueObjects" Version="2.x.x" />
<PackageVersion Include="FunctionalDdd.PrimitiveValueObjectGenerator" Version="2.x.x" />

<!-- After -->
<PackageVersion Include="Trellis.Results" Version="3.x.x" />
<PackageVersion Include="Trellis.DomainDrivenDesign" Version="3.x.x" />
<PackageVersion Include="Trellis.Asp" Version="3.x.x" />
<PackageVersion Include="Trellis.Primitives" Version="3.x.x" />
<PackageVersion Include="Trellis.Primitives.Generator" Version="3.x.x" />
<PackageVersion Include="Trellis.Analyzers" Version="3.x.x" />

Otherwise, update each .csproj file individually.

2. Update Using Statements

Global find-and-replace in source files:

Find	Replace
`using FunctionalDdd;`	`using Trellis;`
`using FunctionalDdd.PrimitiveValueObjects;`	`using Trellis;`

All types are now in the Trellis namespace.

3. Update OpenTelemetry Method Names

If you use auto-instrumentation:

Find	Replace
`.AddFunctionalDddRopInstrumentation()`	`.AddResultsInstrumentation()`
`.AddFunctionalDddCvoInstrumentation()`	`.AddPrimitiveValueObjectInstrumentation()`

4. Build and Test

dotnet build
dotnet test

The compiler and Trellis.Analyzers will flag any issues. All types, methods, and behaviors remain identical — only the namespace and package names have changed.

No API Changes

All public APIs are identical between FunctionalDdd v2 and Trellis v3:

Result<T>, Maybe<T>, all error types — unchanged
Bind, Map, Tap, Ensure, Match, Combine — unchanged
Aggregate<T>, Entity<T>, ValueObject — unchanged
RequiredString, RequiredGuid, RequiredInt, RequiredDecimal — unchanged
ToActionResult(), ToHttpResult() — unchanged
All async extensions — unchanged

Deprecation Notice

The old FunctionalDdd.* NuGet packages will be deprecated (not unlisted) with a pointer to the corresponding Trellis.* package. Existing code using the old packages will continue to work, but no new features or bug fixes will be applied to the old packages.

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