HashSet<T>.Add(T) Method

Definition

Namespace:

System.Collections.Generic

Assemblies:

netstandard.dll, System.Collections.dll

Source:

HashSet.cs

Adds the specified element to a set.

C#

public bool Add(T item);

Parameters

item

T

The element to add to the set.

Returns

Boolean

true if the element is added to the HashSet<T> object; false if the element is already present.

Implements

Add(T)

Examples

The following example demonstrates how to create and populate two HashSet<T> objects. This example is part of a larger example provided for the UnionWith method.

C#

HashSet<int> evenNumbers = new HashSet<int>();
HashSet<int> oddNumbers = new HashSet<int>();

for (int i = 0; i < 5; i++)
{
    // Populate numbers with just even numbers.
    evenNumbers.Add(i * 2);

    // Populate oddNumbers with just odd numbers.
    oddNumbers.Add((i * 2) + 1);
}

Remarks

If Count already equals the capacity of the HashSet<T> object, the capacity is automatically adjusted to accommodate the new item.

If Count is less than the capacity of the internal array, this method is an O(1) operation. If the HashSet<T> object must be resized, this method becomes an O(n) operation, where n is Count.

Applies to