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Welcome to UnionGenerator

Powerful discriminated unions for C# with zero runtime overhead.

UnionGenerator brings type-safe, compile-time discriminated unions to C# using Roslyn source generators. Build robust applications with exhaustive pattern matching, eliminate boilerplate, and make invalid states impossible.

Why UnionGenerator?​

// ✅ Type-safe, explicit, and exhaustive
[GenerateUnion]
public partial class Result<T, E>
{
    public static Result<T, E> Ok(T value) => new OkCase(value);
    public static Result<T, E> Error(E error) => new ErrorCase(error);
}

var result = await FetchDataAsync();
return result.Match(
    ok: data => Ok(data),
    error: err => BadRequest(err.Message)
);

Key Features​

  • 🔥 Zero Boilerplate: Define unions with just an attribute
  • ⚡ Zero Runtime Cost: Pure compile-time code generation
  • 🛡️ Type-Safe: Compiler enforces exhaustive pattern matching
  • 🔌 Framework Integration: ASP.NET Core, EF Core, FluentValidation
  • 📖 Full IDE Support: IntelliSense, debugging, refactoring

Installation​

dotnet add package UnionGenerator

View all packages →

Quick Example​

[GenerateUnion]
public partial class Result<T, E>
{
    public static Result<T, E> Ok(T value) => new OkCase(value);
    public static Result<T, E> Error(E error) => new ErrorCase(error);
}

public IActionResult GetUser(int id)
{
    var result = _service.GetUser(id);
    return result.Match(
        ok: user => Ok(user),
        error: msg => NotFound(msg)
    );
}

Next Steps​

  1. What is UnionGenerator? - Understand the core concepts
  2. Why Discriminated Unions? - Learn the benefits
  3. Quick Start - Build your first union in 5 minutes

Ready to build safer, more expressive C# code? Get started →