OptionSharp

Another option for options in C#

Disclaimer: If you are looking for a stable, production ready lib you are better off using something like LanguageExt.Core.

Motivation

This library is primarily for myself to learn about functional programming but also takes a different opinion/approach compared to other more well established libs.

• Focuses only on Option and Result types
• Does not allow for null
• Uses records as discriminated unions which is as close as you can get in c# whilst still being idiomatic (AFAIK)
• Rust-like (ish) feel, promotes the use of strongly typed errors
• Source generated code to keep it readable

Usage

Define your error types as below which will generate some constructor methods for convenience

[GenerateResult("Handle")]
public abstract record HandleError;

public sealed record FailedToDeserialize(string Message) : HandleError;
public sealed record InvalidId(int Id) : HandleError;

Return options and results in your domain

public Result<int, HandleError> TryGetIdOnlyIfSeven(int id) => 
        id == 7 
            ? Handle.Ok(id) 
            : Handle.Err<int>(new InvalidId(id));

Use extension methods to operate on values in a functional way

var eight = TryGetIdOnlyIfSeven(7)
    .Inspect(seven => Console.WriteLine($"seven is {seven}"))
    .Map(seven => seven + 1)
    .UnwrapOrDefault(0);