HashSet Collection in C#

An unordered collection of unique items is known as a HashSet. It is found in System.Collections.Generic namespace. Some of the features of HashSet Collection are as follows:

1. The HashSet Collection provides operations with high performance.
2. There are no duplicate elements in the HashSet Collection.
3. There is no maximum capacity for the elements in the HashSet. The capacity increases as the number of number of elements increase.
4. There is no particular order of the elements in the HashSet Collection.

Constructors in HashSet Collection

The different constructors and their description is given as follows:

Table: Constructors in HashSet Collection in C#

Source: MSDN

Properties in HashSet Collection

The different properties and their description is given as follows:

Table: Properties in HashSet Collection in C#

Source: MSDN

Methods in HashSet Collection

The different methods and their description is given as follows:

Table: Methods in HashSet Collection in C#

Source: MSDN

HashSet Operations

Some of the operations in a HashSet are given as follows:

Adding Elements in HashSet

The Add() method can be used to add elements into a HashSet. The program that demonstrates this is given as follows:

Source Code: Program to add elements in HashSet in C#

using System;
using System.Collections.Generic;
namespace HashSetDemo
{   
    class Example
     {
        static void Main(string[] args)
       {
           HashSet<int> set1 = new HashSet<int>();

           for (int i = 1; i <= 10; i++)
           {
               set1.Add(i);
           }

           Console.WriteLine("The first 10 natural numbers are:");
           foreach (int i in set1)
           {
               Console.WriteLine(i);
           }
       }
   }
}

The output of the above program is given below:

The first 10 natural numbers are:
1
2
3
4
5
6
7
8
9
10

Printing Elements of HashSet

The elements of the Hashset can be printed using the foreach loop. A program for this is given below:

Source Code: Program to print elements in HashSet in C#

using System;
using System.Collections.Generic;
namespace HashSetDemo
{   class Example
   { static void Main(string[] args)
       {
           HashSet<int> set1 = new HashSet<int>();
           for (int i = 1; i <= 10; i++)
           {
               set1.Add(i);
           }
           Console.WriteLine("The even numbers in the HashSet are:");
           foreach (int i in set1)
           {
               if(i%2 == 0)
               {
                   Console.WriteLine(i);
               }
           }
       }
   }
}

The output of the above program is given below:

The even numbers in the HashSet are:
2
4
6
8
10

Removing Elements from HashSet

The Remove() method can be used to remove elements from a HashSet. The program that demonstrates this is given as follows:

Source Code: Program to remove elements in HashSet in C#

using System;
using System.Collections.Generic;
namespace HashSetDemo
{   class Example
   { static void Main(string[] args)
       {
           HashSet<int> set1 = new HashSet<int>();

           for (int i = 1; i <= 10; i++)
           {
               set1.Add(i);
           }
           Console.WriteLine("The elements in the HashSet are:");
           foreach (int i in set1)
           {
               Console.WriteLine(i);
           }
           for (int i = 1; i <= 10; i++)
           {
               if(i%2 == 0)
               {
                   set1.Remove(i);
               }
           }
           Console.WriteLine("The odd elements in the HashSet are:");
           foreach (int i in set1)
           {
               Console.WriteLine(i);
           }
       }
   }
}

The output of the above program is given below:

The elements in the HashSet are:
1
2
3
4
5
6
7
8
9
10
The odd elements in the HashSet are:
1
3
5
7
9

Finding an element in HashSet

The Contains method finds if an element is present in HashSet ot ot. If it is present, Contains() returns TRUE and otherwise it returns FALSE.

The program that demonstrates this is given as follows:

Source Code: Program to find element in HashSet in C#

using System;
using System.Collections.Generic;
namespace HashSetDemo
{   class Example
   { static void Main(string[] args)
       {
           HashSet<int> set1 = new HashSet<int>();
           for (int i = 1; i <= 10; i++)
           {
               set1.Add(i);
           }
           Console.WriteLine("The elements in the HashSet are:");
           foreach (int i in set1)
           {
               Console.WriteLine(i);
           }
           Console.WriteLine("5 is present in HashSet: " + set1.Contains(5));
           Console.WriteLine("50 is present in HashSet: " + set1.Contains(50));
       }
   }
}

The output of the above program is given below:

The elements in the HashSet are:
1
2
3
4
5
6
7
8
9
10

5 is present in HashSet: True
50 is present in HashSet: False