C# | Union of SortedSet to a collection

Last Updated : 11 Jul, 2025
SortedSet class represents the collection of objects in sorted order. This class comes under the System.Collections.Generic namespace. SortedSet<T>.UnionWith(IEnumerable<T>) method is used to modify the current SortedSet<T> object so that it contains all elements that are present in either the current object or the specified collection. Properties:
  • In C#, SortedSet class can be used to store, remove or view elements.
  • It maintains ascending order and does not store duplicate elements.
  • It is suggested to use SortedSet class if you have to store unique elements and maintain ascending order.
Syntax: 
mySortedSet1.UnionWith(mySortedSet2);
Here, mySortedSet1 and mySortedSet2 are two SortedSet objects. Exception: This method will give ArgumentNullException if the SortedSet is null. Below given are some examples to understand the implementation in a better way: Example 1: CSHARP 
// C# code to get the Union of 2 SortedSets
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a SortedSet of integers
        SortedSet<int> mySortedSet1 = new SortedSet<int>();

        // adding elements in mySortedSet1
        mySortedSet1.Add(2);
        mySortedSet1.Add(4);
        mySortedSet1.Add(6);
        mySortedSet1.Add(8);
        mySortedSet1.Add(10);

        // Creating a SortedSet of integers
        SortedSet<int> mySortedSet2 = new SortedSet<int>();

        // adding elements in mySortedSet
        mySortedSet2.Add(4);
        mySortedSet2.Add(5);
        mySortedSet2.Add(7);
        mySortedSet2.Add(8);
        mySortedSet2.Add(9);

        Console.WriteLine("The union of mySortedSet1 and mySortedSet2 is: ");

        mySortedSet1.UnionWith(mySortedSet2);

        // To display the union of mySortedSet1 and mySortedSet2
        foreach(int i in mySortedSet1)
        {
            Console.WriteLine(i);
        }
    }
}
Output: 
The union of mySortedSet1 and mySortedSet2 is: 
2
4
5
6
7
8
9
10
Example 2: CSHARP 
// C# code to get the Union of 2 SortedSets
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a SortedSet of strings
        SortedSet<string> mySortedSet1 = new SortedSet<string>();

        // adding elements in mySortedSet1
        mySortedSet1.Add("Geeks");
        mySortedSet1.Add("for");
        mySortedSet1.Add("Geeks");
        mySortedSet1.Add("Noida");
        mySortedSet1.Add("Data Structures");

        // Creating a SortedSet of strings
        SortedSet<string> mySortedSet2 = new SortedSet<string>();

        // adding elements in mySortedSet
        mySortedSet2.Add("Geeks");
        mySortedSet2.Add("Java");
        mySortedSet2.Add("Geeks Classes");
        mySortedSet2.Add("C++");
        mySortedSet2.Add("Noida");

        Console.WriteLine("The union of mySortedSet1 and mySortedSet2 is: ");

        mySortedSet1.UnionWith(mySortedSet2);

        // To display the union of mySortedSet1 and mySortedSet2
        foreach(string str in mySortedSet1)
        {
            Console.WriteLine(str);
        }
    }
}
Output: 
The union of mySortedSet1 and mySortedSet2 is: 
C++
Data Structures
for
Geeks
Geeks Classes
Java
Noida
Reference:
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