C# | Remove the specified element from a HashSet

01 Feb, 2019
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<T>.Remove(T) method is used to removes the specified element from a HashSet<T> object.
Syntax:
public bool Remove (T item);

Here, item is the element which is to be remove.
Return Value: The method returns True if the element is successfully found and removed and returns False if item is not found in the HashSet<T> object.
Below examples illustrate the use of HashSet.Remove(T) Method:
Example 1:
// C# code to remove the specified // element from a HashSetusing System;using System.Collections.Generic;  class GFG {      // Driver code    public static void Main()    {          // Creating a HashSet of integers        HashSet<int> mySet = new HashSet<int>();          // Inserting even numbers less than        // equal to 20 in HashSet mySet        for (int i = 0; i < 10; i++) {            mySet.Add(i * 2);        }          Console.WriteLine("The elements in HashSet are : ");          // Displaying the elements in HashSet        foreach(int i in mySet)        {            Console.WriteLine(i);        }          // Displaying the number of elements in HashSet        Console.WriteLine("Number of elements are : " + mySet.Count);          // Removing the element 10 if present        if (mySet.Contains(10)) {            mySet.Remove(10);        }          Console.WriteLine("The elements in HashSet are : ");          // Displaying the elements in HashSet        foreach(int i in mySet)        {            Console.WriteLine(i);        }          // Displaying the number of elements in HashSet        Console.WriteLine("Number of elements are : " + mySet.Count);    }}
The elements in HashSet are : 
0
2
4
6
8
10
12
14
16
18
Number of elements are : 10
The elements in HashSet are : 
0
2
4
6
8
12
14
16
18
Number of elements are : 9

Example 2:
// C# code to remove the specified//  element from a HashSetusing System;using System.Collections.Generic;  class GFG {      // Driver code    public static void Main()    {          // Creating a HashSet of strings        HashSet<string> mySet = new HashSet<string>();          // Inserting elements into HashSet        mySet.Add("Data Structures");        mySet.Add("Algorithms");        mySet.Add("Java");        mySet.Add("Puzzles");        mySet.Add("Coding");          Console.WriteLine("The elements in HashSet are : ");          // Displaying the elements in HashSet        foreach(string i in mySet)        {            Console.WriteLine(i);        }          // Displaying the number of elements in HashSet        Console.WriteLine("Number of elements are : " + mySet.Count);          // Removing the element "JavaScript" if present        if (mySet.Contains("JavaScript")) {            mySet.Remove("JavaScript");        }          Console.WriteLine("The elements in HashSet are : ");          // Displaying the elements in HashSet        foreach(string i in mySet)        {            Console.WriteLine(i);        }          // Displaying the number of elements in HashSet        Console.WriteLine("Number of elements are : " + mySet.Count);    }}
The elements in HashSet are : 
Data Structures
Algorithms
Java
Puzzles
Coding
Number of elements are : 5
The elements in HashSet are : 
Data Structures
Algorithms
Java
Puzzles
Coding
Number of elements are : 5

Reference:
https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.hashset-1.remove?view=netframework-4.7.2
CSharp-Generic-HashSet
CSharp-Generic-Namespace
CSharp-method
C#
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