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SortedSet in C#

Last Updated : 11 Sep, 2025
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SortedSet<T> is a collection of unique elements that are automatically sorted in ascending order by default. It is implemented using a balanced binary search tree (red-black tree), which provides efficient insertion, deletion and search operations.

There are some key features mentioned below:

  • Unique and Sorted: Automatically stores elements without duplicates in sorted order.
  • Set Operations: Supports mathematical operations such as UnionWith, IntersectWith and ExceptWith.
  • Optimal: Add, Remove and Contains operations have O(log n) time complexity.

Creating a SortedSet

Step 1: Include System.Collections.Generic namespace

using System.Collections.Generic;

Step 2: Create a SortedSet using the SortedSet Class

SortedSet<type_of_sortedset> sortedset_name = new SortedSet<type_of_sortedset>();

Example:

C# 
using System; using System.Collections.Generic; class Geeks {  static void Main() {  // Create a SortedSet using collection initializer  SortedSet<int> numbers = new SortedSet<int> { 7, 1, 2, 8, 1, 4 };  // Add elements  numbers.Add(6);  // Attempt to add duplicate (will not be added)  numbers.Add(2);  Console.WriteLine("SortedSet elements:");  foreach (int num in numbers)  Console.Write(num + " ");  } }

Output
SortedSet elements: 1 2 4 6 7 8

Note: Duplicate elements are automatically ignored.

Performing Different Operations on SortedSet

1. Adding Element

  • Add(): We can use the Add method to put elements in the sorted set
  • Collection-Initializer: Using the collection initializer we can directly put the element with initialization.

// Using the Add() method
SortedSet<int> num= new SortedSet<int>();
num.Add(1);
num.Add(2);

// Using Collection Initalizer
SortedSet<int> num = new SortedSet<int> { 2, 1, 4,3 };

2. Accessing Elements

Using foreach loop: We can use for loop to Iterate each element to access the the sorted set.

SortedSet<int> numbers= new SortedSet<int> { 2,3,4,5};

foreach (int num in numbers)

Console.WriteLine(num);

Using ForEach loop with Lambda Expressions: Lambda expressions reduces the number of code lines and enhances the code readability.

SortedSet<int> numbers = new SortedSet<int> { 2, 3, 4, 5 };

numbers.ToList().ForEach(n => Console.WriteLine(n));

Using ElementAt() with LINQ: The SortedSet does not directly support the Indexes but we can use LINQ and use ElementAt() method.

using System.Linq;


SortedSet<int> numbers= new SortedSet<int> { 2,3,4,5 };
Console.WriteLine(numbers.ElementAt(0));

Example: Accessing Elements Using Different Methods

C# 
using System; using System.Linq; using System.Collections.Generic; class Geeks {  static void Main() {    // Creating a SortedSet using Collection Initializer  SortedSet<int> num = new SortedSet<int> { 2, 3, 4, 5 };  // Accessing elements using foreach loop  Console.WriteLine("Accessing using foreach loop:");  foreach (int ele in num)  Console.Write(ele + " ");  Console.WriteLine();  // Creating a SortedSet using Add() method  SortedSet<int> num2 = new SortedSet<int>();  num2.Add(1);  num2.Add(2);  num2.Add(3);  // Accessing elements using ForEach loop  Console.WriteLine("Accessing using ForEach loop:");  num2.ToList().ForEach(ele => Console.Write(ele + " "));  Console.WriteLine();  } }

Output
Accessing using foreach loop: 2 3 4 5 Accessing using ForEach loop: 1 2 3

3. Removing Elements

SortedSet<T> provides three ways to remove elements:

Example:

C# 
using System; using System.Collections.Generic; class Geeks {  static public void Main() {  // Creating a SortedSet  SortedSet<int> set = new SortedSet<int>();  // Adding elements to the SortedSet  set.Add(1);  set.Add(2);  set.Add(3);  set.Add(4);  // Display total elements before removal  Console.WriteLine("Total number of elements present in set: {0}", set.Count);  // Remove a specific element  set.Remove(1);  // Display total elements after removing one element  Console.WriteLine("Total number of elements present in set after Remove(1): {0}", set.Count);  // Remove all elements using Clear method  set.Clear();  // Display total elements after clearing the set  Console.WriteLine("Total number of elements present in set after Clear(): {0}", set.Count);  } }

Output
Total number of elements present in set: 4 Total number of elements present in set after Remove(1): 3 Total number of elements present in set after Clear(): 0

4. Check If an Element Exists

We can check the presence of an specific element using the Contains method.

Example:

C# 
using System; using System.Collections.Generic; public class Geeks{ static public void Main() { // Creating SortedSet using SortedSet class SortedSet<int> set = new SortedSet<int>(); // Add the elements in SortedSet using Add method  set.Add(1);  set.Add(2);  set.Add(3);  set.Add(4);    // Check if the element exists in the SortedSet if (set.Contains(1)) Console.WriteLine("Element is available."); else Console.WriteLine("Element is not available."); } }

Output
Element is available.

A

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