迭代器中GetEnumberator的问题

Question

我现在在学习集合，书上的这个例子,请问下为什么说Primes类不包含GetEnumberator的公共定义，以至Main函数里的foreach不能用Primes的变量？
谢谢了！
[code]
public class Primes
    {
        private long min, max;
        public Primes()
            : this(2, 100)
        { 
        }
        public Primes(long minimum, long maximum)
        {
            if (min < 2)
            {
                min = 2;
            }
            min = minimum;
            max = maximum;
        }
        public IEnumerator GetEnumberator()
        {
            
            for (long possiblePrime = min; possiblePrime <= max; possiblePrime++)
            {
                bool isPrime = true;
                for (long possibleFactor = 2; possiblePrime <= (long)Math.Floor(Math.Sqrt(possiblePrime)); possibleFactor++)
                {
                    long remainderAfterDivision = possiblePrime % possibleFactor;
                    if (remainderAfterDivision == 0)
                    {
                        isPrime = false;
                        break;
                    }
                }
                if (isPrime)
                {
                    yield return possiblePrime;
                }
            }
        }
    }
[/code][code]
static void Main(string[] args)
        {
            Primes primesForm2To1000 = new Primes(2, 1000);
            foreach (long i in primesForm2To1000)
                Console.WriteLine("{0}", i);
            Console.ReadKey();
        }
[/code]

Answer 1

 public class Primes
    {
        private long min, max;
        public Primes()
            : this(2, 100)
        { 
        }
        public Primes(long minimum, long maximum)
        {
            if (min < 2)
            {
                min = 2;
            }
            min = minimum;
            max = maximum;
        }
        public IEnumerator GetEnumberator()
        {
            
            for (long possiblePrime = min; possiblePrime <= max; possiblePrime++)
            {
                bool isPrime = true;
                for (long possibleFactor = 2; possiblePrime <= (long)Math.Floor(Math.Sqrt(possiblePrime)); possibleFactor++)
                {
                    long remainderAfterDivision = possiblePrime % possibleFactor;
                    if (remainderAfterDivision == 0)
                    {
                        isPrime = false;
                        break;
                    }
                }
                if (isPrime)
                {
                    yield return possiblePrime;
                }
            }
        }
    }
 static void Main(string[] args)
        {
            Primes primesForm2To1000 = new Primes(2, 1000);
            foreach (long i in primesForm2To1000)
                Console.WriteLine("{0}", i);
            Console.ReadKey();
        }