C # uses the yield keyword to enable a custom collection to implement a foreach traversal method

The foreach traversal is a common feature of C #, and this article demonstrates the way in which C # uses the yield keyword to enable a custom collection to implement a foreach traversal. The steps are as follows:

In general, when we create a custom collection, we can only implement the IEnumerable interface (and possibly the IEnumerator interface) in order for it to support the foreach traversal.

But we can also implement a foreach traversal by using an iterator method built with the yield keyword, and the custom collection does not implement the IEnumerable interface

Attention:

Although you do not need to implement the IEnumerable interface, the iterator's method must be named GetEnumerator () and the return value must be of type IEnumerator.

The instance code and a simple comment are described below:

Class person{public    string Name;    public void Sayhi ()    {      Console.WriteLine (' Hello: {0} ', this. Name);}    } A very simple custom collection (--Simple to add, delete, indexer, etc.) does not implement the IEnumerable interface Class personlist{  person[] pers =new person[4];  Public Personlist ()  {    Pers[0] = new Person () {Name = "1"};    PERS[1] = new Person () {Name = "2"};    PERS[2] = new Person () {Name = "3"};    PERS[3] = new Person () {Name = "4"};  } Simple iterator method public  IEnumerator GetEnumerator ()  {    foreach (person item in pers)    {      //yield The return function is to return an element of the collection and move to the next element      yield return item;}}  Class program{  static void Main (string[] args)  {    personlist list = new Personlist ();    foreach (person item in list)    {      item. Sayhi ();    }    Console.ReadLine ();  }}

Interested readers can do a hands-on test of this example code, I believe there will be a new harvest.

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C # uses the yield keyword to enable a custom collection to implement a foreach traversal method

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C # uses the yield keyword to enable a custom collection to implement a foreach traversal method