C # the principle that the class can be traversed through foreach,

C # the principle that the class can be traversed through foreach,

Conditions that must be met first for the class to be traversed using foreach

1. The class must implement the public method public IEnumerator GetEnumerator () {}. you can also inherit the IEnumerable interface to implement this method.

2. The class implements public IEnumerator GetEnumerator () {}. to return an object for traversal, this object must inherit the IEnumerator interface.

1 class Program 2 {3 static void Main (string [] args) 4 {5 Person p = new Person (); 6 p [0] = "James "; 7 p [1] = "xiao hong"; 8 p [2] = "Xiao Fang"; 9 p [3] = "Xiao Long"; 10 for (int I = 0; I <p. count; I ++) 11 {12 Console. writeLine (p [I]); 13} 14 15 Console. writeLine ("========================================== ===== "); 17 foreach (var name in p) 18 {19 Console. writeLine (name); 20} 21 Console. readKey (); 22} 23} 24 25 internal class Person: IEnumerable26 {27 private List <string> listStudent = new List <string> (); 28 public int Count {29 get {return listStudent. count;} 30} 31 32 public string this [int index] 33 {34 get {return listStudent [index];} 35 set36 {37 if (index> = Count) 38 {39 listStudent. add (value); 40} 41 else42 {43 listStudent [index] = value; 44} 45} 46} 47 48 49 50 public IEnumerator GetEnumerator () 51 {52 return new PersonIEnumerator (listStudent); 53} 54} 55 56 class PersonIEnumerator: IEnumerator57 {58 public PersonIEnumerator (List <string> _ listName) 59 {60 listName = _ listName; 61} 62 63 private List <string> listName; 64 private int index =-1; 65 66 public object Current67 {68 get {return listName [index];} 69} 70 71 public bool MoveNext () 72 {73 index ++; 74 if (index> = listName. count) 75 {76 return false; 77} 78 else79 {80 return true; 81} 82} 83 84 public void Reset () 85 {86 index =-1; 87} 88}