Queue and Queue are first-in first-out (FIFO) data structures, providing methods to Enqueue (add an item to the tail of the queue) and Dequeue (retrieve and remove the item at the head of the queue). A Peek method is also provided to return the element at the head of the queue without removing it, and a Count property.
The generic version of Queue has the following methods:
public class Queue : IEnumerable, ICollection, IEnumerable
{
public Queue();
public Queue (IEnumerable collection); // Copies existing elements
public Queue (int capacity); // To lessen auto-resizing
public void Clear();
public bool Contains (T item);
public void CopyTo (T[] array, int arrayIndex);
public int Count { get; }
public T Dequeue();
public void Enqueue (T item);
public Enumerator GetEnumerator(); // To support foreach
public T Peek();
public T[] ToArray();
public void TrimExcess();
}
The following is an example of using Queue:
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
class Sample
{
public static void Main()
{
var q = new Queue();
q.Enqueue(10);
q.Enqueue(20);
int[] data = q.ToArray(); // Exports to an array
Console.WriteLine (q.Count);
Console.WriteLine (q.Peek());
Console.WriteLine(q.Dequeue());
Console.WriteLine (q.Dequeue());
Console.WriteLine(q.Dequeue());
}
}
The output:
2
10
10
20
Unhandled Exception: System.InvalidOperationException: Queue empty.
at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resour
ce)
at System.Collections.Generic.Queue`1.Dequeue()
at Sample.Main() in c:\g\Program.cs:line 18