Sample.cs

using System;

namespace RSpecExample
{
    public class Sample
    {
        public Sample(params string[] words)
        {
            Words = words;
        }

        public string[] Words { get; private set; }

        public string Greet()
        {
            return "Hello " + string.Join(",", Words);
        }

        public string Exec(Func<string[], string> block)
        {
            return block(Words);
        }
    }
}

sample_spec.rb

require 'rubygems'
require 'spec'
require File.dirname(__FILE__) + '/../src/RSpecExample/bin/Debug/RSpecExample.dll'

include RSpecExample

describe Sample do
  context "with args 'hoge', 'fuga' and 'piyo'" do
    subject{ Sample.new('hoge', 'fuga', 'piyo') }
    its(:Greet){ should == 'Hello hoge,fuga,piyo' }
    it{ should have(3).Words }
    it{ subject.Exec(lambda{|s| System::String.Join('-', s)}).should == 'hoge-fuga-piyo' }
    it{ subject.Exec(lambda{|(a, b, c)| a[0] + b[0] + c[0]}).should == 'hfp' }
  end
end