Simple optional type for .NET
Get Started
$ dotnet add package Infrastructure.OptionReadme
Usage
Get the NuGet package: Infrastructure.Option on NuGet
Overview
The purpose of the Infrastructure.Option is to help you write code that is easier to read and understand.
The Infrastructure.Option makes it explicit when a value might be missing, but it stays out of your sight when irrelevant.
Option<T>presents the situation when you don't know if the value is present or not.Option.Some<T>tells that the value of typeTis present.Option.None<T>tells that the value of typeTis not present.
Option.Some<T> behaves like the object of type T, and you can, e.g., pass it directly to a method accepting a parameter of type T.
Option.None<T> means that the value is not present so you cannot even accidentally try to access it.
The Option provides fluent access to the underlying optional value with Choose() and Otherwise().
Choose()applied to a single object selects the chosen property or returns null.Choose()applied to a collection selects the underlying values, i.e., those of typeSome<T>.Otherwise()defines fallback behavior when encounteringNone<T>.
For more information about option types, see Option type on Wikipedia.
JSON Serialization
Infrastructure.Option supports JSON serialization using System.Text.Json without requiring any additional dependencies.
The Option<T> type is serialized as an object with a single ValueOrNull property.
The OpenAPI documentation support is also provided without any additional dependencies.
For example, Option.Some("Hello!") is serialized as:
{ "valueOrNull": "Hello!" }
ToString()
ToString() called on Option.Some returns the result of the underlying object's ToString().
ToString() called on Option.None returns an empty string.
Examples
Basic usage
using Infrastructure;
using System;
void Print(string value) => Console.WriteLine(value);
var something = Option.Some("Something");
var nothing = Option<string>.None;
Print(something); // something is implicitly cast to string.
// Print(nothing); // This does not compile
Creating Options
var some = Option.Some("Example value");
var none = Option.None<string>();
Pattern matching
using Infrastructure;
using System;
var option = Option.Some("Example value");
var value = option switch
{
{ Value: {} some } => some,
_ => "Something else"
};
Console.WriteLine(value); // Prints: Example value
Choose() underlying value
using Infrastructure;
using System;
Option<Country> optionalCountry = new Country("Finland");
var nameOfTheCountry = optionalCountry.Choose(country => country.Name); // nameOfTheCountry is of type Option<string>
Console.WriteLine(nameOfTheCountry); // Prints: Finland
record Country(string Name);
Fallback with Otherwise()
var option = Option.None<string>();
var result = option.Otherwise("Something else"); // result == "Something else"
Choose() underlying values from collections
var collection = new Option<string>[] {
Option.None<string>(),
Option.Some("1"),
Option.None<string>(),
Option.Some("2"),
Option.None<string>(),
Option.Some("3"),
Option.None<string>(),
};
var values = collection.Choose(); // values == [ "1", "2", "3" ]
var first = collection.ChooseFirst(); // first == "1"
Choose() underlying values from collections with mapping
record ExampleType(string ExampleProperty);
var collection = new[] {
Option.None<ExampleType>(),
Option.Some(new ExampleType("1")),
Option.None<ExampleType>(),
Option.Some(new ExampleType("2")),
Option.None<ExampleType>(),
Option.Some(new ExampleType("3")),
Option.None<ExampleType>(),
};
var values = collection.Choose(entry => entry.ExampleProperty); // values == [ "1", "2", "3" ]
var chosen = await collection.Choose(async entry => await Task.FromResult(entry.ExampleProperty)); // chosen == [ "1", "2", "3" ]
Pick singular value from collections
var collection = new Option<string>[] {
Option.Some("1"),
Option.Some("2"),
Option.Some("3")
};
var first = collection.FirstOrNone(); // first == "1"
var firstMatch = collection.FirstOrNone(element => element == "2"); // firstMatch == "2"
var only = collection.SingleOrNone(); // first == "1"
var onlyMatch = collection.SingleOrNone(element => element == "2"); // firstMatch == "2"
Checking if value matches the given predicate
var option = Option.Some("Example value");
var holds = option.Holds(example => example == "Example value"); // holds == true