Upgrading from previous v1.9

WIP. Need to show how to modify the parsing calls from old v1.9 to new v2.x

Version 2 uses only two attributes to describe option syntax: Option and Value·

Option works much like in previous versions, but it can be applied to scalar or sequence values (IEnumerable<T>).

When applied to sequences you can also define Min and Max properties to specify a range of values.

Value resembles ValueOption and ValueList from previous versions. Akin to the new Option attribute, it can be applied to sequences, and now support the Required property too.

[Value] Attribute

Values are partitioned by index. For example:

class Options {
  [Value(0)]
  public int IntValue { get; set; }

  [Value(1, Min=1, Max=3)]
  public IEnumerable<string> StringSeq { get; set; }

  [Value(2)]
  public double DoubleValue { get; set; }
}

So long as you supply values, they will be set to corresponding properties:

$ app 10 str1 str2 str3 1.1

If you omit Min and Max constraints, all available values will be captured by the sequence. There's no point defining a Value attribute with a higher index than that of a sequence Value which lacks a Max range constraint:

class Options {
  [Value(0)]
  public int IntValue { get; set; }

  [Value(1)]
  public IEnumerable<string> StringSeq { get; set; }

  // all values captured by previous specifications,
  // this property will never receive a value
  [Value(2)]
  public DoubleValue { get; set; }
}

[Option] Attribute

If you Omit the option name the long name will be inferred from the member's name.

class Options {
  [Option]
  public string UserId { get; set; }
}

This allows:

$ app --userid=root

Option attribute also supports a Separator property to mimic the deprecated OptionList behavior when applied to sequences.

class Options {
  [Option('t', Separator=':')]
  public IEnumerable<string> Types { get; set; }
}

This allows:

$ app -t int:long:string