Collection Extensions

public static class CollectionExtensions
{
   public static bool IsEmpty<T>(this ICollection<T> collection) // say what you want to extension
    {
      return collection.Count = 0;
    }

   public static void AddRange<T>(this ICollection<T> collection, IEnumerable<T> values)
    {
      foreach(T value in values)
       {
         collection.Add(value);
       }
    }
       // And now every ICollection has these both methods
}