C# | HashSet Class

A HashSet<T> 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.

Characteristics of HashSet Class:

• The HashSet<T> class provides high-performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order.
• The capacity of a HashSet<T> object is the number of elements that the object can hold.
• A HashSet<T> object’s capacity automatically increases as elements are added to the object.
• A HashSet<T> collection is not sorted and cannot contain duplicate elements.
• HashSet<T> provides many mathematical set operations, such as set addition (unions) and set subtraction.

Constructors

Example:

// C# code to create a 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:

1 3 5 7 9

HashSet collection is used for storing the unique value, because HashSet doesn’t contain the duplicate value.

HashSet<T> hset=new HashSet<T>();

using System;

using System.Collections.Generic;

public class Program

{

 public static void Main()

 {

  HashSet<int> hset=new HashSet<int>();

  Random rand=new Random();

  for( int i=0; i<10; i++)

  {

   hset.Add(rand.Next(50,100));

  }

  Console.WriteLine('Duplicate data will not show in the list :');

  foreach(var item in hset)

   Console.WriteLine(item);

 }

}

Duplicate data will not show in the list :

87

85

54

73

56

75

50