C# | Get an enumerator that iterates through the List - GeeksforGeeks

01 Feb, 2019
List<T>.GetEnumerator Method is used to returns an enumerator that iterates through the List<T>.
Syntax:
public System.Collections.Generic.List<T>.Enumerator GetEnumerator ();
Return Value: It returns an List<T>Enumerator for the List<T>.
Below programs illustrate the use of List<T>.GetEnumerator Method:
Example 1:
// C# code to get an enumerator// that iterates through the List<T>.using System;using System.Collections.Generic;  class GFG {      // Driver code    public static void Main()    {          // Creating a List of int        List<int> mylist = new List<int>();          // Inserting elements into List        mylist.Add(45);        mylist.Add(78);        mylist.Add(32);        mylist.Add(231);        mylist.Add(123);        mylist.Add(76);        mylist.Add(726);        mylist.Add(716);        mylist.Add(876);          // To get an Enumerator        // for the List.        List<int>.Enumerator em = mylist.GetEnumerator();        display(em);    }      // display method    static void display(IEnumerator<int> em)    {        while (em.MoveNext()) {            int val = em.Current;            Console.WriteLine(val);        }    }}
Output:
45
78
32
231
123
76
726
716
876

Example 2:
// C# code to get an enumerator// that iterates through the List<T>.using System;using System.Collections.Generic;  class GFG {      // Driver code    public static void Main()    {          // Creating a List of string        List<string> mylist = new List<string>();          // Inserting elements into List        mylist.Add("C#");        mylist.Add("Java");        mylist.Add("C");        mylist.Add("C++");          // To get an Enumerator        // for the List.        List<string>.Enumerator em = mylist.GetEnumerator();        display(em);    }      // display method    static void display(IEnumerator<string> em)    {        while (em.MoveNext()) {            string val = em.Current;            Console.WriteLine(val);        }    }}
Output:
C#
Java
C
C++

Note:
The foreach statement of the C# language hides the complexity of the enumerators. Therefore, using foreach is recommended, instead of directly manipulating the enumerator.
Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.
Current returns the same object until either MoveNext or Reset is called. MoveNext sets Current to the next element.
An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and its behavior is undefined.
This method is an O(1) operation.
Reference:
https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1.getenumerator?view=netframework-4.7.2
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