Mutually Exclusive Options

You can define options as belonging to a set that is mutually exclusive. Consider an imaginary application that can act as either a web or ftp server, but not both at the same time.

Defining the options class as follows:

class Options
{
  [Option(MutuallyExclusiveSet = "web")]
  public string DocumentRoot { get; set; }

  [Option(MutuallyExclusiveSet = "web")]
  public bool EnableJavaScript { get; set; }

  [Option(MutuallyExclusiveSet = "ftp")]
  public string FtpDirectory { get; set; }

  [Option(MutuallyExclusiveSet = "ftp")]
  public bool AnonymousLogin { get; set; }
}

and group options in different set. In this way if you combine an ftp option with a web one, parsing will fail.

;; permitted
$ app --enablejavascript --documentroot ~/var/local/website

;; denied
$ app --anonymouslogin --enablejavascript

If you have various sets and each set contains a good number of options, It's better to structure your application with Verb Commands.