horsdal

public class Option<T>
{
  public T Value { get; private set; }
  public bool IsSome { get { return this != None; } }

  public static readonly Option<T> None = new Option<T>(default(T));
  public static Option<T> Some(T value)
  {
    return new Option<T>(value);
  }

horsdal

var name = Option<string>.Some("hello");
var noName = Option<string>.None;

horsdal

[Fact]
public void MatchOptionSome()
{
  var name = Option<string>.Some("hello");

  var greeting = name.Match(
    some: n => n,
    none: () => "phew"
  );

horsdal

public TRes Match<TRes>(Func<T, TRes> some, Func<TRes> none)
{
  if (IsSome)
    return some.Invoke(Value);
  else
    return none.Invoke();
}
    
public void Match(Action<T> some, Action none)
{

horsdal

public class Option<T> : IEnumerable<T>
{
  public T Value { get; private set; }
  public bool IsSome { get { return this != None; } }

  public static readonly Option<T> None = new Option<T>(default(T));
  public static Option<T> Some(T value)
  {
    return new Option<T>(value);
  }

horsdal

public static class OptionHelpers
{
  public static Option<T> AsOption<T>(this IEnumerable<T> enu)
  {
    var val = enu.FirstOrDefault();
    if (!enu.Any() || Equals(val, null))
      return Option<T>.None;
    else
      return Option<T>.Some(val);
  }

horsdal

public IEnumerator<T> GetEnumerator()
{
  if (IsSome)
    yield return Value;
}

IEnumerator IEnumerable.GetEnumerator()
{
  return GetEnumerator();
}

horsdal

[Fact]
public void PassSomeThroughLinq()
{
  var name = Option<string>.Some("christian");
  var mangledName = name.Select(n => n + " " + n )
                         .Select(r => r.Replace('i', 'X'))
                         .Take(1)
                         .AsOption();

  Assert.True(mangledName.IsSome);

horsdal

public class Option<T>
{
  public T Value { get; private set; }
  public bool IsSome { get { return this != None; } }

  public static readonly Option<T> None = new Option<T>(default(T));
  public static Option<T> Some(T value)
  {
    return new Option<T>(value);
  }

horsdal

public static class OptionHelpers
{
  public static TRes Match<T, TRes>(this Option<T> self, Func<T, TRes> some, Func<TRes> none)
  {
    if (self.IsSome)
      return some.Invoke(self.Value);
    else
      return none.Invoke();
  }