A Maybe type for C#, aimed as an idiomatic port of the option type in F# to C#

JFlepp.Maybe

A Maybe type for C#, aimed as an idiomatic port of the option type in F# to C#.

An option type is a type that has two states, Some and None. You can use it instead of null values as it forces you to check if a value exists before using it. It also allows you to to enter an elevated world of having a value or not.

An easy way to think about option types is as lists with one item or none. This library provides you with such a type and with C# idiomatic extensions as you find them in System.Linq.

Take a look the the Microsoft Docs for more informations about the option type this library aims to provide.

Take a look at the [API](docs/API.md) or [special cases](docs/SpecialCases.md) docs for more information.

Hello World example

var aValue = Maybe.Some("Hello ")
    .Select(v => v + "World!");

void WriteIfIsSome(Maybe<string> option) => option.ForEach(Console.WriteLine);

WriteIfIsSome(aValue);

// Hello World!

Contributing

Feel free to open issues and PRs!

Developing

You can develop this library using Visual Studio 2019. Simply open the JFlepp.Maybe.sln solution from the root directory and you're good to go.

There is a CI pipeline set up that must pass before you can merge a PR.

QA

There already are many implementations of the option type in C# available. Why another one?

There are many other implementations around and all differentiate a little bit. This implementation aims to implemented option methods in an C# idiomatic (mainly System.Linq like) way and doing so in a straight forward manner.

I don't want to introduce a funky library into my domain model. Which quality gates are set up?

There are several quality checks set up to assure the stability of this library. All checks are being enforced in the CI pipeline.

• Test Code Coverage of a least 99%.
• Microsoft.CodeAnalysis.FxCopAnalyzers analyzers are set up.
• No build warnings are allowed.
• The public API is fully documented, and there is a [API documentation](docs/API.md) set up.

I'm stuck on the .NET framework. Am I still able to use this library?

This library provides in addition the the netstandard2.0 target a net45 target. So yes, you are able to use this library in your .NET Framework app without any hassle.

How does versioning work?

This library uses SemVer for versioning.

How do I access the value of a Maybe?

If possible, try to stay in the elevated world of maybes. Do not try to get the value out of a maybe until you actually need it, but let it be a part of your domain model instead. Try to use the numerous extension methods provided on the maybe if possible while doing so.

Nevertheless, there is an extension method hidden inside another namespace that allows direct value access

namespace JFlepp.Functional.Unsafe
{
    public static class MaybeExtensions
    {
        public static T GetValue<T>(this Maybe<T> maybe);
    }
}

References

• FSharp on MSDN
• FSharp.Core