C# | Create HashSet from another collection
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:
C#
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); } } } |
Output
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:
CSHARP
// 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:
CSHARP
// 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); } } } |
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