C# | Remove elements from a SortedSet that match the predicate

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>.RemoveWhere(Predicate<T>) Method is used to remove all elements that match the conditions defined by the specified predicate from a SortedSet<T>. 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: 
public int RemoveWhere (Predicate<T> match);
Return Value: This method returns the number of elements that were removed from the SortedSet<T> collection. Exception: This method will give ArgumentNullException if the match is null. Note: Calling this method is an O(n) operation, where n is Count i.e, the number of elements that are contained in the SortedSet. Below are the examples to illustrate the SortedSet<T>.RemoveWhere(Predicate<T>) Method Example 1: CSHARP 
// C# code to remove elements from a SortedSet
// that match the predicate
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

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

        // Inserting elements into SortedSet
        for (int i = 0; i < 10; i++) {
            mySet.Add(i);
        }

        Console.WriteLine("The elements in SortedSet are : ");

        // Displaying the elements in SortedSet
        foreach(int i in mySet)
        {
            Console.WriteLine(i);
        }

        // Displaying the number of elements in SortedSet
        Console.WriteLine("Number of elements are : " + mySet.Count);

        // Remove elements from a SortedSet
        // with conditions defined by the predicate
        mySet.RemoveWhere(isEven);

        Console.WriteLine("The elements in SortedSet are : ");

        // Displaying the elements in SortedSet
        foreach(int i in mySet)
        {
            Console.WriteLine(i);
        }

        // Displaying the number of elements in SortedSet
        Console.WriteLine("Number of elements are : " + mySet.Count);
    }

    // Helper function which tells
    // whether an element is even or not
    private static bool isEven(int i)
    {
        return ((i % 2) == 0);
    }
}
Output: 
The elements in SortedSet are : 
0
1
2
3
4
5
6
7
8
9
Number of elements are : 10
The elements in SortedSet are : 
1
3
5
7
9
Number of elements are : 5
Example 2 : CSHARP 
// C# code to remove elements from a
// SortedSet that match the predicate
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

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

        // Inserting elements into SortedSet
        for (int i = 0; i < 20; i++) {
            mySet.Add(i);
        }

        // Displaying the number of elements in SortedSet
        Console.WriteLine("Number of elements are : " + mySet.Count);

        // Remove elements from a SortedSet
        // with conditions defined by the predicate
        mySet.RemoveWhere(myFunc);

        // Displaying the number of elements in SortedSet
        Console.WriteLine("Number of elements are : " + mySet.Count);
    }

    // Helper function which tells
    // whether an element is divisible
    // by both 2 and 3
    private static bool myFunc(int i)
    {
        return ((i % 2) == 0 && (i % 3 == 0));
    }
}
Output: 
Number of elements are : 20
Number of elements are : 16
Reference:
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