Initialize a HashSet in C#

This post will discuss how to initialize a HashSet<T> in C#.

We can use object initializers to initialize a HashSet<T> in C#, introduced in C# 3.0. It consists of a sequence of elements, enclosed within { and } where each member is separated by a comma. This causes each of the specified elements to be added to the HashSet<T> object, without explicitly invoking the constructor.

The following example shows how to initialize a new HashSet<int> by using object initializers.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

HashSet<int> numbers = new HashSet<int>() { 1, 2, 3 };

Console.WriteLine(String.Join(", ", numbers)); // 1, 2, 3

}

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Alternatively, you can invoke the HashSet<T> constructor to initialize a new instance of the HashSet<T> class with elements of the specified collection. For example, the following code initializes a HashSet<T> with distinct elements of a List<T>, in no particular order.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> collection = new List<int>() { 1, 3, 2, 1 };

HashSet<int> numbers = new HashSet<int>(collection);

Console.WriteLine(String.Join(", ", numbers)); // 1, 3, 2

}

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If you need to add the specified element to an existing HashSet<int> object, consider using the standard Add method. The following code example demonstrates this:

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

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

numbers.Add(1);

numbers.Add(2);

numbers.Add(3);

Console.WriteLine(String.Join(", ", numbers)); // 1, 2, 3

}

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That’s all about initializing a HashSet<T> in C#.

Initialize a HashSet in C#

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