Question 1

How to handle errors with OneOf in C#?

Accepted Answer

Use OneOf to return typed error objects from methods instead of throwing exceptions. Define a union like OneOf<Success, ErrorType1, ErrorType2> and use the Match method to handle each case explicitly, ensuring compile-time safety and clearer error flows.

Question 2

OneOf vs exceptions for control flow?

Accepted Answer

OneOf replaces exceptions with typed returns, making error handling part of the method signature. This avoids the anti-pattern of using exceptions for normal flow and provides better compile-time checks, though it requires more upfront type definitions.

Question 3

Can OneOf work with async methods?

Accepted Answer

Yes, OneOf can be used with async methods by returning Task>. However, matching might require async lambdas in Match or Switch, which can add complexity compared to synchronous code.

Question 4

OneOf compared to C# 9 pattern matching?

Accepted Answer

OneOf provides structured discriminated unions with exhaustive matching, similar to pattern matching but more focused on union types. While C# 9 has improved pattern matching, OneOf offers dedicated compile-time guarantees for defined unions, though it adds library dependency.

Question 5

How to set up the OneOf source generator?

Accepted Answer

Install the OneOf.SourceGenerator NuGet package, then apply the [GenerateOneOf] attribute to a partial class inheriting from OneOfBase. The generator automatically creates boilerplate code like implicit conversions during compilation, reducing manual work.

Question 6

Is OneOf good for large codebases?

Accepted Answer

Yes, OneOf excels in large or brown-field projects by enforcing exhaustive handling, which reduces bugs when adding new types. However, teams should consider the learning curve and ensure it aligns with existing coding standards to avoid integration issues.

OneOf

What is OneOf?

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Frequently Asked Questions