Lifting functions that deal with non-optional values into an Optional context.

UsingApplyOnOption.cs

using System;
using Blackbaud.Registration.Tests.Common.Extensions;
using LanguageExt.UnitTesting;
using Xunit;
using static LanguageExt.Prelude;

namespace Blackbaud.Registration.MessageHandlers.UnitTests.CommandHandlers
{
    public class UsingApplyOnOption
    {
        private class NonFictionBook
        {
            public string Title { get; }
            public string Author { get; }

            public NonFictionBook(string title, string author)
            {
                Title = title;
                Author = author;
            }
        }

        private class FictionBook
        {
            public string BookTitle { get; }
            public string AuthorName { get; }

            public FictionBook(string bookTitle, string authorName)
            {
                BookTitle = bookTitle;
                AuthorName = authorName;
            }
        }

        [Fact]
        public void LiftingNonOptionalFunctionsIntoOptionExample()
        {
            Func<NonFictionBook, FictionBook, bool> writtenBySameAuthor =
                (nonFictionBook, fictionBook) => nonFictionBook.Author == fictionBook.AuthorName;

            writtenBySameAuthor.Apply(
                Some(new NonFictionBook("Cooking for Dummies", "Sarah Smith")),
                Some(new FictionBook("1984", "George Orwell"))
            ).ShouldBeSome(Assert.False);

            writtenBySameAuthor.Apply(
                Some(new NonFictionBook("The Age of Mass Surveillance", "George Orwell")),
                Some(new FictionBook("1984", "George Orwell"))
            ).ShouldBeSome(Assert.True);

            writtenBySameAuthor.Apply(
                Some(new NonFictionBook("The Age of Mass Surveillance", "George Orwell")),
                None
            ).ShouldBeNone();
        }
    }
}