1using System;
 2using System.Collections.Generic;
 3
 4namespace specs
 5{
 6    static public class IllegalExtensions
 7    {
 8        static public void Add<T>(this IEnumerable<T> items, T item)
 9        {
10            var collection = items as ICollection<T>;
11            if (null == collection) throw new ArgumentException("this aint a collection, buddy!");
12            collection.Add(item);
13        }
14    }
15}