C# | Add element to HashSet
Last Updated :
11 Jul, 2025
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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. Elements can be added to HashSet using HashSet.Add(T) Method .
Syntax:
object . If the element is already present then it returns false.
Below given are some examples to understand the implementation in a better way:
Example 1:
CSHARP
CSHARP
mySet.Add(T item);Here mySet is the name of the HashSet. Parameter:
item: The element to add to the set.Return Type: This method returns true if the element is added to the HashSet
// C# code to add element to HashSet
using System;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Creating a HashSet of odd numbers
HashSet<int> odd = new HashSet<int>();
// Inserting elements in HashSet
for (int i = 0; i < 5; i++) {
odd.Add(2 * i + 1);
}
// Displaying the elements in the HashSet
foreach(int i in odd)
{
Console.WriteLine(i);
}
}
}
Output:
Example 2:
1 3 5 7 9
// C# code to add element to HashSet
using 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 in HashSet
mySet.Add("Geeks");
mySet.Add("GeeksforGeeks");
mySet.Add("GeeksClasses");
mySet.Add("GeeksQuiz");
// Displaying the elements in the HashSet
foreach(string i in mySet)
{
Console.WriteLine(i);
}
}
}
Output:
Reference:
Geeks GeeksforGeeks GeeksClasses GeeksQuiz
