Check if an element is in the Queue in C#

To check if an element exists in a Queue in C#, you can use the Contains() method. This method returns true if the specified element is found in the queue, and false otherwise. The Queue<T> class in C# provides this built-in functionality for easy element searching.

Syntax

Following is the syntax for using the Contains() method −

bool result = queue.Contains(element);

Parameters

• element − The element to search for in the queue

Return Value

The method returns a bool value −

• true if the element is found in the queue

• false if the element is not found in the queue

Using Contains() with String Queue

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      Queue<string> queue = new Queue<string>();
      queue.Enqueue("Electronics");
      queue.Enqueue("Accessories");
      queue.Enqueue("Toys");
      queue.Enqueue("Books");
      queue.Enqueue("Furniture");
      queue.Enqueue("Clothing");
      queue.Enqueue("Footwear");
      queue.Enqueue("Cookware");
      queue.Enqueue("Pet Supplies");
      
      Console.WriteLine("Elements in the Queue...");
      foreach(var element in queue) {
         Console.WriteLine(element);
      }
      
      Console.WriteLine("Does the queue contain 'Books'? = " + queue.Contains("Books"));
      Console.WriteLine("Does the queue contain 'Sports'? = " + queue.Contains("Sports"));
   }
}

The output of the above code is −

Elements in the Queue...
Electronics
Accessories
Toys
Books
Furniture
Clothing
Footwear
Cookware
Pet Supplies
Does the queue contain 'Books'? = True
Does the queue contain 'Sports'? = False

Using Contains() with Integer Queue

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      Queue<int> queue = new Queue<int>();
      queue.Enqueue(100);
      queue.Enqueue(200);
      queue.Enqueue(300);
      queue.Enqueue(400);
      queue.Enqueue(500);
      queue.Enqueue(600);
      queue.Enqueue(700);
      queue.Enqueue(800);
      queue.Enqueue(1000);
      
      Console.WriteLine("Elements in the Queue...");
      foreach(var element in queue) {
         Console.WriteLine(element);
      }
      
      Console.WriteLine("Does the queue contain 500? = " + queue.Contains(500));
      Console.WriteLine("Does the queue contain 50? = " + queue.Contains(50));
   }
}

The output of the above code is −

Elements in the Queue...
100
200
300
400
500
600
700
800
1000
Does the queue contain 500? = True
Does the queue contain 50? = False

How It Works

The Contains() method performs a linear search through the queue, comparing each element with the specified value using the default equality comparer for the type. For reference types, it uses reference equality, and for value types, it uses value equality.

Conclusion

The Contains() method provides a simple way to check if an element exists in a C# Queue. It returns true if the element is found and false otherwise, making it easy to perform membership tests on queue collections.