public bool IsAnagram(string s1,string s2)
{
  if (s1.Length != s2.Length)
     return false;
  var s1Array = s1.ToLower().ToCharArray();
  var s2Array = s2.ToLower().ToCharArray();

  Array.Sort(s1Array);
  Array.Sort(s2Array);

  s1 = new string(s1Array);
  s2 = new string(s2Array);

  return s1 == s2;
}