In C#, you can create a HashSet<T> from another collection by using the HashSet<T> constructor that takes an IEnumerable<T> parameter. Here’s an example:
using System;
using System.Collections.Generic;
public class Program
{ public static void Main()
{
// create a List of integers
List< int > numbers = new List< int > { 1, 2, 3, 4, 5 };
// create a HashSet from the List
HashSet< int > numberSet = new HashSet< int >(numbers);
// print out the contents of the HashSet using a foreach loop
Console.WriteLine( "Contents of HashSet:" );
foreach ( int number in numberSet)
{
Console.WriteLine(number);
}
}
} |
Contents of HashSet: 1 2 3 4 5
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. You can create a HashSet from another collection by passing the collection as an argument while creating the object of HashSet. Below given are some examples to understand the implementation in a better way: Example 1:
// C# code to Create HashSet // from another collection using 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 10 in HashSet mySet
for ( int i = 0; i < 5; i++) {
mySet.Add(i * 2);
}
// Creating new HashSet mySet_new from already
// Created HashSet mySet
HashSet< int > mySet_new = new HashSet< int >(mySet);
Console.WriteLine("The elements in newly created HashSet are : ");
// Displaying the elements of newly created HashSet
foreach ( int i in mySet_new)
{
Console.WriteLine(i);
}
}
} |
Example 2:
// C# code to Create HashSet // from another collection 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 into HashSet mySet
mySet.Add("Delhi");
mySet.Add("Noida");
mySet.Add("Chandigarh");
mySet.Add("New York");
mySet.Add("Bangalore");
// Creating new HashSet mySet_new from already
// Created HashSet mySet
HashSet< string > mySet_new = new HashSet< string >(mySet);
Console.WriteLine("The elements in newly created HashSet are : ");
// Displaying the elements of newly created HashSet
foreach ( string i in mySet_new)
{
Console.WriteLine(i);
}
}
} |