In c#, HashSet is a disjoint group of an unique elements. We can a apply a multiple operation on HashSet such as Add, Remove, Contains etc. HashSet is also  allow to apply a standard set of operations such as union, intersection, and symmetric difference.

Syntax for creating a HashSet:

HashSet<int> HSet1 = new HashSet<int>();
HashSet<int> HSet2 = new HashSet<int>();

Code for adding an elements in the HashSet<>:
We use an add() method to add an element to the HashSet.

for (int i = 1; i < =10; i++)
{
   HSet1.Add(2 * i);
}
for (int j = 1; j < =10; j++)
{
   HSet2.Add(100 * j);
}

Code for Printing the elements of HashSet using foreach loop:

namespace HashSetSampleApplication
{
    class ProgramForHashSet
    {
        static void Main(string[] args)
        {
            HashSet<int> HSet1 = new HashSet<int>();
            HashSet<int> HSet2 = new HashSet<int>();
            for (int i = 1; i <=10; i++)
            {
                HSet1.Add(2 * i);
            }
            for (int j = 1; j <=10; j++)
            {
                HSet2.Add(100 * j);
            }
            Console.WriteLine("The table of two(2) is:");
            foreach (int hset1 in HSet1)
            {
                Console.WriteLine(hset1);
            }
            Console.WriteLine("The table of Hundered(100) is:");
            foreach (int hset2 in HSet2)
            {
                Console.WriteLine(hset2);
            }
        }
    }
}

Output:

Code for Removing the elements from the HashSet<>:

namespace HashSetSampleApplication
{
    class ProgramForHashSet
    {
        static void Main(string[] args)
        {
            HashSet<int> HSet = new HashSet<int>();
            for (int i = 1; i <=10; i++)
            {
                HSet.Add(2 * i);
            }
        Console.WriteLine("The table of Two(2) is:");
            foreach (int hset in HSet)
            {
                Console.WriteLine(hset);
            }
          for (int i = 1; i <= 10; i++)
            {
                if (i < 8)
                {
                    HSet.Remove(2 * i);
                }
            }
            Console.WriteLine("After Removing the elements from the hashset :  ");
            foreach (int hset in HSet)
            {
                Console.WriteLine(hset);
            }
        }
    }
}

Output:

Code for finding an element from the HashSet<>:

namespace HashSetSampleApplication
{
    class ProgramForHashSet
    {
        static void Main(string[] args)
        {
            HashSet<int> HSet1 = new HashSet<int>();
            for (int i = 1; i <=10; i++)
            {
                HSet1.Add(2 * i);
            }
            Console.WriteLine("The table of two(2) is:");
            foreach (int hset1 in HSet1)
            {
                Console.WriteLine(hset1);
            }
            Console.WriteLine("ITem 6 is found in HashSet : " + HSet1.Contains(6));
            Console.WriteLine("ITem 10 is found in HashSet : " + HSet1.Contains(10));
            Console.WriteLine("ITem 18 is found in HashSet : " + HSet1.Contains(18));
        }
    }
}

Output: