CondictionalsExtensions

ConditionalsExtensions.cs

public static class CondictionalsExtensions
{
    public static Tuple<bool, T> If<T>(this T src, Predicate<T> p)
    {
        return p(src)
            ? Tuple.Create(true, src)
            : Tuple.Create(false, src);
    }

    public static Tuple<bool, T, R> Then<T, R>(this Tuple<bool, T> src, Func<T, R> f)
    {
        return src.Item1
            ? Tuple.Create(src.Item1, src.Item2, f(src.Item2))
            : Tuple.Create(src.Item1, src.Item2, default(R));
    }

    public static R Else<T,R>(this Tuple<bool, T, R> src, Func<T,R> f)
    {
        return src.Item1
            ? src.Item3
            : f(src.Item2);
    }
}

[TestFixture]
class ConditionalsExtensionsTests
{
    [Test]
    public void Test()
    {
        var result = new[] { 1, 2, 3, 4 }
            .If(x => x.Any())
            .Then(x => $"List contains {x.Count()} elements")
            .Else(_ => "List is empty");

        Check.That(result).IsEqualTo("List contains 4 elements");

        var result2 = new List<int>()
            .If(x => x.Any())
            .Then(x => $"List contains {x.Count()} elements")
            .Else(_ => "List is empty");

        Check.That(result2).IsEqualTo("List is empty");
    }
}