. NET-based iterator

. NET-based iterator
The foreach loop is implemented using the IEnumerator interface. IEnumerator implements the iterator. In foreach, how does one iterate an arrayList set? Call arrayLis. GetEnumberator () to return an IEnumberator reference. Call the MoveNext () method of the returned Enumberator interface. If MoveNext () returns true, a reference of the object is obtained using the Current attribute of the IEnumberator interface for foreach loop. Repeat the previous two steps. If the MoveNext method returns false, the loop stops. Implementation example of the iterator: copy the code class Program {public static void Main (string [] args) {foreach (string str in SimpleList () {Console. writeLine (str);} Console. readKey ();} public static IEnumerable SimpleList () {yield return "1"; yield return "2"; yield return "3 ";}} copy the code to implement the simplest iterator. The result is: QQ20141114211249. A complex example is given below. The prime number is returned using an iterator: copy the code public static void Main (string [] args) {Primes primesFrom2TO1000 = new Primes (2, 1000); foreach (long I in primesFrom2TO1000) {Console. write ("{0}", I) ;}} copy the code copy code public class Primes {private long min; private long max; public Primes (): this (2,200) {} public Primes (long minimum, long maximum) {if (minimum <2) {min = 2;} else {min = minimum ;} Max = maximum;} public System. collections. IEnumerator GetEnumerator () // The return type is an iterator {for (long possiblePrime = min; possiblePrime <= max; possiblePrime ++) {bool isPrime = true; for (long possibleFactor = 2; possibleFactor <= (long) Math. floor (Math. sqrt (possiblePrime); possibleFactor ++) {long remainderAfterDivsion = possiblePrime % possibleFactor; if (remainderAfterDivsion = 0) {isPrime = f Alse; break ;}}if (isPrime) {yield return possiblePrime; // returns the prime number }}}. The result of copying the code is: QQ20141114212209. There are two types returned by the iterator: IEnumberable and IEnumerator. To iterate a class, you can use GetEnumerator (). Its return type is IEnumerator. If you want to iterate a class member, such as a method, use IEnumerable.