Queue.Equals() Method in C#

The Queue.Equals() method in C# is used to determine whether the specified object is equal to the current queue instance. This method performs reference equality comparison, not content comparison, meaning it returns true only if both variables refer to the same queue object in memory.

Syntax

Following is the syntax for the Queue.Equals() method −

public virtual bool Equals(object obj);

Parameters

• obj − The object to compare with the current queue instance.

Return Value

Returns true if the specified object is the same instance as the current queue; otherwise, false.

Using Equals() for Reference Comparison

The Equals() method checks if two queue references point to the same object, not whether their contents are identical −

using System;
using System.Collections.Generic;

public class Demo {
    public static void Main() {
        Queue<string> queue = new Queue<string>();
        queue.Enqueue("Gary");
        queue.Enqueue("Jack");
        queue.Enqueue("Ryan");
        queue.Enqueue("Kevin");
        
        // Same reference comparison
        Console.WriteLine("queue.Equals(queue): " + queue.Equals(queue));
        
        // Create another queue with same content
        Queue<string> queue2 = new Queue<string>();
        queue2.Enqueue("Gary");
        queue2.Enqueue("Jack");
        queue2.Enqueue("Ryan");
        queue2.Enqueue("Kevin");
        
        // Different reference comparison
        Console.WriteLine("queue.Equals(queue2): " + queue.Equals(queue2));
        
        // Assign same reference
        Queue<string> queue3 = queue;
        Console.WriteLine("queue.Equals(queue3): " + queue.Equals(queue3));
    }
}

The output of the above code is −

queue.Equals(queue): True
queue.Equals(queue2): False
queue.Equals(queue3): True

Using Equals() with Non-Generic Queue

using System;
using System.Collections;

public class Demo {
    public static void Main() {
        Queue queue = new Queue();
        queue.Enqueue(100);
        queue.Enqueue(200);
        queue.Enqueue(300);
        queue.Enqueue(400);
        
        Queue queue2 = new Queue();
        queue2.Enqueue(100);
        queue2.Enqueue(200);
        queue2.Enqueue(300);
        queue2.Enqueue(400);
        
        Console.WriteLine("Different instances with same content:");
        Console.WriteLine("queue.Equals(queue2): " + queue.Equals(queue2));
        
        Console.WriteLine("\nSame instance comparison:");
        Console.WriteLine("queue.Equals(queue): " + queue.Equals(queue));
        
        Console.WriteLine("\nComparing with null:");
        Console.WriteLine("queue.Equals(null): " + queue.Equals(null));
    }
}

The output of the above code is −

Different instances with same content:
queue.Equals(queue2): False

Same instance comparison:
queue.Equals(queue): True

Comparing with null:
queue.Equals(null): False

Key Points

• Queue.Equals() performs reference equality, not content equality.

• Returns true only when comparing a queue with itself or another variable pointing to the same queue object.

• Two different queue instances with identical content will return false.

• Comparing with null always returns false.

Conclusion

The Queue.Equals() method in C# checks for reference equality rather than content equality. It returns true only when both queue variables refer to the exact same object instance in memory, making it useful for identity checks rather than content comparison.