gistfile1.cs

class DefaultNullable<A,B> {
  public delegate B MapFunc(A input);

  private A underlying;

  public DefaultNullable(A input) {
    this.underlying = input;
  }

  public static implicit operator DefaultNullable<A,B>(A input) {
    return new DefaultNullable<A,B>(input);
  }

  public B getDefault(MapFunc f, B defaultVal) {
    if (underlying == null) {
      return f(underlying);
    } else {
      return defaultVal;
    }
  }
}

Doh. Didn't remember that "in" is a keyword :P

This is what I get for doing my coding in gist instead of actually trying to use an IDE