C# | Check if HashSet and the specified collection contain the same elements

Last Updated : 11 Jul, 2025

Here's an example code that demonstrates how to use the Overlaps method to check if a HashSet and a specified collection share common elements in C#:

using System;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        // Create a HashSet and a List
        HashSet<int> set1 = new HashSet<int> { 1, 2, 3, 4, 5 };
        List<int> list1 = new List<int> { 5, 6, 7, 8 };

        // Check if the HashSet and List contain any common elements
        bool hasOverlap = set1.Overlaps(list1);
        Console.WriteLine("Do set1 and list1 have common elements? " + hasOverlap);

        // Create another List with no common elements
        List<int> list2 = new List<int> { 6, 7, 8 };

        // Check if the HashSet and List2 contain any common elements
        bool hasOverlap2 = set1.Overlaps(list2);
        Console.WriteLine("Do set1 and list2 have common elements? " + hasOverlap2);

        Console.ReadLine();
    }
}

Output

Do set1 and list1 have common elements? True
Do set1 and list2 have common elements? False

A HashSet is an unordered collection of the unique elements. It comes under System.Collections.Generic namespace. It is used in a situation where we want to prevent duplicates from being inserted in the collection. As far as performance is concerned, it is better in comparison to the list. HashSet.SetEquals(IEnumerable) Method is used to check if a HashSet and the specified collection contain the same elements or not.

Syntax:

mySet1.SetEquals(mySet2);

Here, mySet1 and mySet2 are HashSets objects.

Return Type: This method return True if the mySet1 is equal to mySet2 else returns False.

Exception: This method will give ArgumentNullException if the HashSet is null.

Below given are some examples to understand the implementation in a better way:

Example 1:

CSHARP

// C# code to check if HashSet and the specified
// collection contain the same elements.
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a HashSet of strings
        HashSet<string> mySet1 = new HashSet<string>();

        // Inserting elements in HashSet
        mySet1.Add("Geeks");
        mySet1.Add("GeeksforGeeks");
        mySet1.Add("GeeksClasses");
        mySet1.Add("GeeksQuiz");

        // Creating a HashSet of strings
        HashSet<string> mySet2 = new HashSet<string>();

        // Inserting elements in HashSet
        mySet2.Add("Geeks");
        mySet2.Add("GeeksforGeeks");
        mySet2.Add("GeeksClasses");
        mySet2.Add("GeeksQuiz");

        // Check if both HashSets contains same elements
        Console.WriteLine(mySet1.SetEquals(mySet2));
    }
}

Example 2:

CSHARP

// C# code to check if HashSet and the specified
// collection contain the same elements.
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a HashSet of integers
        HashSet<int> mySet1 = new HashSet<int>();

        // Inserting elements in HashSet
        mySet1.Add(4);
        mySet1.Add(8);
        mySet1.Add(12);
        mySet1.Add(16);

        // Creating a HashSet of integers
        HashSet<int> mySet2 = new HashSet<int>();

        // Inserting elements in HashSet
        mySet2.Add(5);
        mySet2.Add(10);
        mySet2.Add(15);
        mySet2.Add(20);

        // Check if both HashSets contains same elements
        Console.WriteLine(mySet1.SetEquals(mySet2));
    }
}