Why am I getting errors here ?

namespace Treehouse.CodeChallenges
{
    class FrogStats
    {
        public static double GetAverageTongueLength(Frog[] frogs)
        {
            double sum = 0;
            for(Frog i in frogs)
            {
                sum += i.TongueLength;
            }
            return sum;
        }
    }
}

namespace Treehouse.CodeChallenges
{
    public class Frog
    {
        public int TongueLength { get; }

        public Frog(int tongueLength)
        {
            TongueLength = tongueLength;
        }
    }
}