Queue Collection in C#

The Queue Collection is used when the data items need to be arranged in a FIFO (First In First Out) manner. When a data item is entered into the collection, it is called enqueue. When the data item is removed from the collection, it is called dequeue.

Constructors in Queue Collection

The different constructors and their description is given as follows:

Table: Constructors in Queue Collection in C#

Properties in Queue Collection

The different properties and their description is given as follows:

Table: Properties in Queue Collection in C#

Methods in Queue Collection

The different methods and their description is given as follows:

Table: Methods in Queue Collection in C#

Source: MSDN

Queue Operations

Some of the stack operations are given as follows:

Enqueue

An element is added to the end of the queue using the Enqueue() method. The program that demonstrates this is given as follows:

Source Code: Program to enqueue elements in Queue in C#

using System;
using System.Collections;
namespace QueueDemo
{
  class Example
  {
     static void Main(string[] args)
     {
        Queue q = new Queue();
        q.Enqueue(1);
        q.Enqueue(2);
        q.Enqueue(3);
        q.Enqueue(4);
        Console.WriteLine("Queue elements are:");
        foreach (int i in q)
        {
            Console.Write(i + " ");
        }
     }
  }
}

The output of the above program is as follows:

Queue elements are:
1 2 3 4

Dequeue

The element at the beginning of the queue can be removed using the Dequeue() method. The program that demonstrates this is given as follows:

Source Code: Program to dequeue elements in Queue in C#

using System;
using System.Collections;
namespace QueueDemo
{
  class Example
  {
     static void Main(string[] args)
     {
        Queue q = new Queue();
        q.Enqueue(1);
        q.Enqueue(2);
        q.Enqueue(3);
        q.Enqueue(4);
        Console.Write("Original queue: ");
        foreach (int i in q)
        {
            Console.Write(i + " ");
        }
        q.Dequeue();
        q.Dequeue();
        Console.WriteLine();
        Console.Write("Queue after Dequeue() operation: ");
        foreach (int i in q)
        {
            Console.Write(i + " ");
        }
     }
  }
}

The output of the above program is as follows:

Original queue: 1 2 3 4
Queue after Dequeue() operation: 3 4

Peek

The element at the beginning of the queue can be viewed without removing it using the Peek() method. The program that demonstrates this is given as follows:

Source Code: Program to peek beginning element in Queue in C#

using System;
using System.Collections;
namespace QueueDemo
{
  class Example
  {
     static void Main(string[] args)
     {
        Queue q = new Queue();
        q.Enqueue(1);
        q.Enqueue(2);
        q.Enqueue(3);
        q.Enqueue(4);
        Console.Write("Queue elements are: ");
        foreach (int i in q)
        {
            Console.Write(i + " ");
        }
        Console.WriteLine();
        Console.Write("Element at the beginning of the queue is: {0}", q.Peek());
     }
  }
}

The output of the above program is as follows:

Queue elements are: 1 2 3 4
Element at the beginning of the queue is: 1

Count the number of elements in a Queue

To count the number of elements in a Queue, use the Count property:

Source Code: Program to count the number of elements in a Queue in C#

using System;
using System.Collections;

namespace QueueExample {
  class Example {
     static void Main(string[] args) {
        Queue q = new Queue();
        
        q.Enqueue('A');
        q.Enqueue('B');
        q.Enqueue('C');
        q.Enqueue('D');
        q.Enqueue('E');
        q.Enqueue('F');
        q.Enqueue('G');
        q.Enqueue('H');
        
        Console.WriteLine("Count = {0} ", q.Count);
        
        Console.ReadKey();
     }
  }
}

The output of the above program is as follows:

Count = 8