Conversion between List and HashSet in C#

This post will discuss how to convert a List to HashSet in C# and vice versa.

Convert `List` to `HashSet`:

1. Using `HashSet` Constructor

We can use the HashSet constructor, which takes an IEnumerable<T> to construct a new instance of the HashSet<T> class containing distinct elements of the list.

Note that since HashSet contains distinct elements, it’ll discard any repeated elements in the list.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> list = new List<int> { 1, 3, 3, 2, 4 };

HashSet<int> set = new HashSet<int>(list);

Console.WriteLine(String.Join(",", set));

}

Output: 1,3,2,4

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2. `Enumerable.ToHashSet()` method (`System.Linq`)

We can use ToHashSet() method to create a HashSet<T> from an IEnumerable<T>.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> list = new List<int> { 1, 3, 3, 2, 4 };

HashSet<int> set = list.ToHashSet();

Console.WriteLine(String.Join(",", set));

}

Output: 1,3,2,4

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Convert `HashSet` to `List`:

1. Using `List` Constructor

We can use the List constructor, which takes an IEnumerable<T> to construct a new instance of the List<T> containing all elements of the set.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

HashSet<int> set = new HashSet<int> { 1, 2, 3, 4, 5 };

List<int> list = new List<int>(set);

Console.WriteLine(String.Join(",", list));

}

Output: 1,2,3,4,5

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2. `Enumerable.ToList()` method (`System.Linq`)

We can use ToList() method to create a List<T> from an IEnumerable<T>.

using System;

using System.Collections.Generic;

using System.Linq;

public class Example

{

public static void Main()

{

HashSet<int> set = new HashSet<int> { 1, 2, 3, 4, 5 };

List<int> list = set.ToList();

Console.WriteLine(String.Join(",", list));

}

Output: 1,2,3,4,5

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That’s all about conversion between List and HashSet in C#.

Conversion between List and HashSet in C#

Convert List to HashSet:

1. Using HashSet Constructor

2. Enumerable.ToHashSet() method (System.Linq)

Convert HashSet to List:

1. Using List Constructor

2. Enumerable.ToList() method (System.Linq)

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Convert `List` to `HashSet`:

1. Using `HashSet` Constructor

2. `Enumerable.ToHashSet()` method (`System.Linq`)

Convert `HashSet` to `List`:

1. Using `List` Constructor

2. `Enumerable.ToList()` method (`System.Linq`)