Is Perfect Square for BigInteger

For testing if an integer is a perfect square

   private bool IsPerfectSquare(BigInteger n)
   {
        
        var sqrt =  (BigInteger)Math.Round(Math.Exp(BigInteger.Log(n) / 2));
 return (sqrt * sqrt) == n;
    }

I took it from http://msdn.microsoft.com/en-us/library/dd268263(v=vs.110).aspx