Functional Extensions for C#

This library helps write code in more functional way. To get to know more about the principles behind it, check out the Applying Functional Principles in C# Pluralsight course.

Installation

Available on nuget

PM> Install-Package CSharpFunctionalExtensions

.NET 4.0 version Installation

~~.NET 4.0 version is available as a separate package on nuget~~

No need for a separate 4.0 package anymore! Use the regular CSharpFunctionalExtensions

Testing

For extension methods on top of this library's Result and Maybe that you can use in tests, see this nuget package (GitHub link: https://github.com/pedromtcosta/FluentAssertions.CSharpFunctionalExtensions).

Example:

// Arrange
var myClass = new MyClass();

// Act
Result result = myClass.TheMethod();

// Assert
result.Should().BeSuccess();

Get rid of primitive obsession

Result<CustomerName> name = CustomerName.Create(model.Name);
Result<Email> email = Email.Create(model.PrimaryEmail);

Result result = Result.Combine(name, email);
if (result.IsFailure)
    return Error(result.Error);

var customer = new Customer(name.Value, email.Value);

Make nulls explicit with the Maybe type

Maybe<Customer> customerOrNothing = _customerRepository.GetById(id);
if (customerOrNothing.HasNoValue)
    return Error("Customer with such Id is not found: " + id);

Compose multiple operations in a single chain

return _customerRepository.GetById(id)
    .ToResult("Customer with such Id is not found: " + id)
    .Ensure(customer => customer.CanBePromoted(), "The customer has the highest status possible")
    .Tap(customer => customer.Promote())
    .Tap(customer => _emailGateway.SendPromotionNotification(customer.PrimaryEmail, customer.Status))
    .Finally(result => result.IsSuccess ? Ok() : Error(result.Error));

Wrap multiple operations in a TransactionScope

return _customerRepository.GetById(id)
    .ToResult("Customer with such Id is not found: " + id)
    .Ensure(customer => customer.CanBePromoted(), "The customer has the highest status possible")
    .WithTransactionScope(customer => Result.Success(customer)
        .Tap(customer => customer.Promote())
        .Tap(customer => customer.ClearAppointments()))
    .Tap(customer => _emailGateway.SendPromotionNotification(customer.PrimaryEmail, customer.Status))
    .Finally(result => result.IsSuccess ? Ok() : Error(result.Error));

Readings and watchings

Contributors

A big thanks to the project contributors!

MateuszW99/CSharpFunctionalExtensions