Getting enumerator that iterates through the Queue in C# - GeeksforGeeks

28 Jan, 2019
Queue<T>.GetEnumerator Method is used to get an enumerator which can iterate through the Queue. And it comes under the System.Collections.Generic namespace.
Syntax:
public System.Collections.Generic.Queue<T>.Enumerator GetEnumerator ();
Below programs illustrate the use of the above-discussed method:
Example 1:
// C# code to illustrate the// Queue<T>.GetEnumerator Methodusing System;using System.Collections.Generic;  class GFG {      // Driver code    public static void Main()    {          // Creating an Queue of strings        Queue<string> myq = new Queue<string>();          // Adding elements to Queue        myq.Enqueue("A");        myq.Enqueue("B");        myq.Enqueue("C");        myq.Enqueue("D");        myq.Enqueue("E");        myq.Enqueue("F");          // To get an Enumerator        // for the Queue        IEnumerator<string> enumerator =                     myq.GetEnumerator();          // If MoveNext passes the end of the        // collection, the enumerator is positioned        // after the last element in the Queue        // and MoveNext returns false.        while (enumerator.MoveNext()) {              Console.WriteLine(enumerator.Current);        }    }}
A
B
C
D
E
F

Example 2:
// C# code to illustrate the// Queue<T>.GetEnumerator Methodusing System;using System.Collections.Generic;  class GFG {      // Driver code    public static void Main()    {          // Creating an Queue of integers        Queue<int> myq = new Queue<int>();          // Adding elements to Queue        myq.Enqueue(78);        myq.Enqueue(84);        myq.Enqueue(44);        myq.Enqueue(77);        myq.Enqueue(99);          // To get an Enumerator        // for the Queue        IEnumerator<int> enumerator =                  myq.GetEnumerator();          // If MoveNext passes the end of the        // collection, the enumerator is positioned        // after the last element in the Queue        // and MoveNext returns false.        while (enumerator.MoveNext()) {              Console.WriteLine(enumerator.Current);        }    }}
78
84
44
77
99

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.queue-1.getenumerator?view=netframework-4.7.2
CSharp-Generic-Namespace
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