Mayhaps value, mayhaps not.

Mayhaps.cs

public abstract class Mayhaps<T>
{
  private Mayhaps() {}
  
  public abstract bool HasValue { get; }

  public abstract T Value { get; }

  public abstract Mayhaps<TR> Map<TR>(Func<T, TR> f);

  private class MayhapsValue : Mayhaps<T>
  {
    private readonly T _value;
    
    public MayhapsValue(T value)
    {
      if (value == null) { 
        throw new ArgumentNullException("Begone, null!"); 
      }
      
      _value = value;
    }
    
    public override bool HasValue
    {
      get { return true; }
    }

    public override T Value
    {
      get { return _value; }
    }

    public override Mayhaps<TR> Map<TR>(Func<T, TR> f)
    {  
      return Mayhaps<TR>.Indeed(f(_value));
    }
  }

  private class MayhapsNothing : Mayhaps<T>
  {
    public override bool HasValue
    {
      get { return false; }
    }

    public override T Value
    { get { throw new InvalidOperationException("Nothing here."); } }

    public override Mayhaps<TR> Map<TR>(Func<T, TR> f)
    {
      return Mayhaps<TR>.Nothing;
    }
  }

  private static MayhapsNothing _nothing = new MayhapsNothing();

  public static Mayhaps<T> Indeed(T value)
  {
    return new MayhapsValue(value);
  }

  public static Mayhaps<T> Nothing
  {
    get { return _nothing; }
  }
}