Generates all permutations of a set by using LINQ and a recursive approach

get-permutations.cs

public static class Permutations
{
    public static IEnumerable<IEnumerable<T>> Get<T>(IEnumerable<T> set, IEnumerable<T> subset = null)
    {
        if (subset == null) subset = new T[] { };
        if (!set.Any()) yield return subset;

        for (var i = 0; i < set.Count(); i++)
        {
            var newSubset = set.Take(i).Concat(set.Skip(i + 1));
            foreach (var permutation in Get(newSubset, subset.Concat(set.Skip(i).Take(1))))
            {
                yield return permutation;
            }
        }
    }
}

Nice. However can be shortened to:

  public static IEnumerable<IEnumerable<T>> Get<T>(this IEnumerable<T> set, IEnumerable<T> subset = null)
  {
    subset = subset ?? Enumerable.Empty<T>();
		
    return set.Any()
      ? set.SelectMany((s,i) => Get(set.Take(i).Concat(set.Skip(i + 1)), subset.Concat(EnumerableEx.Return(s))))
      : EnumerableEx.Return(subset);
  }