The `HashSet<T>` generic class in the ```System.Collections.Generic``` namespace provides the **`Clear()` method**, which is used to remove all the elements from a HashSet<T> in C#. The ```HashSet<T>``` becomes empty after the ```Clear()``` method is called.

# Syntax
```
public void Clear ();
```

- Other object references from elements of the ```HashSet<T>``` are also released after calling the ```Clear()``` method.
- The HashSet's ```Count``` property becomes #key# 0 :zero #key# after the ```Clear()``` method is called.
- This method does not change the *capacity* of the HashSet<T>.

- This method changes the *state* of the HashSet.

In the example below, we first create a HashSet of strings and add two strings to it: `January` and `February`. We then print the count of elements in the HashSet.

Next, we call the `Clear()` method to remove all elements of the HashSet. We again print the count and observe zero after the ```Clear()``` method is called.

The program prints the following output and exits.

```
Added 'January' and 'February' to HashSet, Count : 2
Count of HashSet afte Clear() : 0
```

using System;
using System.Collections.Generic;

class HashSetAdd
{
    static void Main()
    {
       HashSet<string> monthSet = new HashSet<string>();
       monthSet.Add("January");
       monthSet.Add("February");
       Console.WriteLine($"Added 'January' and 'February' to HashSet, Count : {monthSet.Count}");
       monthSet.Clear();
       Console.WriteLine($"Count of HashSet afte Clear() : {monthSet.Count}");
    }
}

How to remove all elements from the HashSet in C#

Use the Clear() method on a HashSet<T> in C# to remove all elements and reset the count to zero.