C# Queue Example

Queue is related to System.Collections.Generic namespace. In, Queue Elements are added to the back (enqueue) and removed from the front (dequeue) of the queue. This is a First-In-First-Out (FIFO) data structure approach.

Features with queue in C#:

• Creating a Queue:

  You need to import the System.Collections.Generic namespace to work with the Queue. To create a Queue, you can use the following code:

  Example

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  using System.Collections.Generic;

  Queue<int> queuefruitprices = new Queue<int>();

  Queue<string> queuefruitnames = new Queue<string>();

  using System.Collections.Generic;

  Queue<int> queuefruitprices = new Queue<int>();

  Queue<string> queuefruitnames = new Queue<string>();

• Enqueueing Elements:

  You can add elements to the back of the Queue using the Enqueue method:

  Example

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  // inserting integer elements

  queuefruitprices.Enqueue(12);

  queuefruitprices.Enqueue(16);

  queuefruitprices.Enqueue(22);

  queuefruitprices.Enqueue(28);

  queuefruitprices.Enqueue(9);

  // inserting string elements

  queuefruitnames.Enqueue("Apple");

  queuefruitnames.Enqueue("Mango");

  queuefruitnames.Enqueue("Cherry");

  queuefruitnames.Enqueue("Orange");

  queuefruitnames.Enqueue("Grape");

  queuefruitnames.Enqueue("Kiwi");

  // inserting integer elements

  queuefruitprices.Enqueue(12);

  queuefruitprices.Enqueue(16);

  queuefruitprices.Enqueue(22);

  queuefruitprices.Enqueue(28);

  queuefruitprices.Enqueue(9);

  // inserting string elements

  queuefruitnames.Enqueue("Apple");

  queuefruitnames.Enqueue("Mango");

  queuefruitnames.Enqueue("Cherry");

  queuefruitnames.Enqueue("Orange");

  queuefruitnames.Enqueue("Grape");

  queuefruitnames.Enqueue("Kiwi");

• Dequeuing Elements:

  You can remove elements from the front of the Queue using the Dequeue method:

  Example

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  // Removes and returns 9

  int frontItem = queuefruitprices.Dequeue();

  // Removes and returns Apple

  string frontItem = queuefruitnames.Dequeue();

  // Removes and returns 9

  int frontItem = queuefruitprices.Dequeue();

  // Removes and returns Apple

  string frontItem = queuefruitnames.Dequeue();

• Peeking at the Front Element:

  You can examine the element at the front of the Queue without removing it using the Peek method:

  Example

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  // Returns 6 (without removing it)

  int frontItem1 = queuefruitprices.Peek();

  // Returns Mango (without removing it)

  string frontItem2 = queuefruitnames.Peek();

  // Returns 6 (without removing it)

  int frontItem1 = queuefruitprices.Peek();

  // Returns Mango (without removing it)

  string frontItem2 = queuefruitnames.Peek();

• Checking if the Queue is Empty:

  You can check if the Queue is empty using the Count property or the IsEmpty property in C# 7.0 and later:

  Example

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  bool isEmpty = queuefruitprices.Count == 0;

  bool isEmpty = queuefruitnames.Count == 0;

  bool isEmpty = queuefruitprices.Count == 0;

  bool isEmpty = queuefruitnames.Count == 0;

• Iterating through a Queue:

  You can use the foreach loop to iterate through the elements in a Queue. This will process the elements in the order they were added:

  Example

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  foreach (int item in queuefruitprices)

  {

  // 9, 6, 12, 5, 18, 22 Prints

  Console.WriteLine(item);

  }

  foreach (string item in queuefruitnames)

  {

  // Prints Apple,Mango,Cherry,Orange,Grape,Kiwi

  Console.WriteLine(item);

  }

  foreach (int item in queuefruitprices)

  {

  // 9, 6, 12, 5, 18, 22 Prints

  Console.WriteLine(item);

  }

  foreach (string item in queuefruitnames)

  {

  // Prints Apple,Mango,Cherry,Orange,Grape,Kiwi

  Console.WriteLine(item);

  }

• Clearing the Queue:

  You can clear the entire Queue using the Clear method:

  Example

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  // Removes all elements from the queue

  queuefruitprices.Clear();

  // Removes all elements from the queue

  queuefruitnames.Clear();

  // Removes all elements from the queue

  queuefruitprices.Clear();

  // Removes all elements from the queue

  queuefruitnames.Clear();

• Queue in C# with Example

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  using System;

  using System.Collections.Generic;

  public class CSharpProgram

  {

  public static void Main(string[] arge)

  {

  Queue<int> queuefruitprices = new Queue<int>();

  Queue<string> queuefruitnames = new Queue<string>();

  queuefruitprices.Enqueue(9);

  queuefruitprices.Enqueue(6);

  queuefruitprices.Enqueue(12);

  queuefruitprices.Enqueue(5);

  queuefruitprices.Enqueue(18);

  queuefruitprices.Enqueue(22);

  queuefruitnames.Enqueue("Apple");

  queuefruitnames.Enqueue("Mango");

  queuefruitnames.Enqueue("Cherry");

  queuefruitnames.Enqueue("Orange");

  queuefruitnames.Enqueue("Grape");

  queuefruitnames.Enqueue("Kiwi");

  foreach (int price in queuefruitprices)

  {

  Console.Write(price + " ");

  }

  Console.WriteLine("\n");

  foreach (string name in queuefruitnames)

  {

  Console.Write(name + " ");

  }

  Console.WriteLine("\n");

  int frontItem1 = queuefruitprices.Dequeue();

  string frontItem2 = queuefruitnames.Dequeue();

  Console.Write(frontItem1 + " ");

  Console.Write(frontItem2 + " ");

  Console.WriteLine("\n");

  int frontItem3 = queuefruitprices.Peek();

  string frontItem4 = queuefruitnames.Peek();

  Console.Write(frontItem3 + " ");

  Console.Write(frontItem4 + " ");

  Console.WriteLine("\n");

  }

  }

  using System;

  using System.Collections.Generic;

  public class CSharpProgram

  {

  public static void Main(string[] arge)

  {

  Queue<int> queuefruitprices = new Queue<int>();

  Queue<string> queuefruitnames = new Queue<string>();

  queuefruitprices.Enqueue(9);

  queuefruitprices.Enqueue(6);

  queuefruitprices.Enqueue(12);

  queuefruitprices.Enqueue(5);

  queuefruitprices.Enqueue(18);

  queuefruitprices.Enqueue(22);

  queuefruitnames.Enqueue("Apple");

  queuefruitnames.Enqueue("Mango");

  queuefruitnames.Enqueue("Cherry");

  queuefruitnames.Enqueue("Orange");

  queuefruitnames.Enqueue("Grape");

  queuefruitnames.Enqueue("Kiwi");

  foreach (int price in queuefruitprices)

  {

  Console.Write(price + " ");

  }

  Console.WriteLine("\n");

  foreach (string name in queuefruitnames)

  {

  Console.Write(name + " ");

  }

  Console.WriteLine("\n");

  int frontItem1 = queuefruitprices.Dequeue();

  string frontItem2 = queuefruitnames.Dequeue();

  Console.Write(frontItem1 + " ");

  Console.Write(frontItem2 + " ");

  Console.WriteLine("\n");

  int frontItem3 = queuefruitprices.Peek();

  string frontItem4 = queuefruitnames.Peek();

  Console.Write(frontItem3 + " ");

  Console.Write(frontItem4 + " ");

  Console.WriteLine("\n");

  }

  }

  
  
  

  Output

  9 6 12 5 18 22

  Apple Mango Cherry Orange Grape Kiwi

  9 Apple

  6 Mango

Summary

Queue is useful when you need to maintain a list of items to be processed in a specific order, where the first item added is the first to be processed.