HashSet<T>.Count Property

Gets the number of elements that are contained in a set.

Namespace:  System.Collections.Generic
Assemblies:   System.Core (in System.Core.dll)
  System.Collections (in System.Collections.dll)

public int Count { get; }

Property Value

Type: System.Int32
The number of elements that are contained in the set.

Implements

ICollection<T>.Count
IReadOnlyCollection<T>.Count

The capacity of a HashSet<T> object is the number of elements that the object can hold. A HashSet<T> object's capacity automatically increases as elements are added to the object.

The capacity is always greater than or equal to Count. If Count exceeds the capacity while adding elements, the capacity is set to the first prime number that is greater than double the previous capacity.

Retrieving the value of this property is an O(1) operation.

The following example demonstrates how to create, populate, and manipulate two HashSet<T> objects. In this example, both the contents of the set and Count display to the console.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        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);
        }

        Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count);
        DisplaySet(evenNumbers);

        Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count);
        DisplaySet(oddNumbers);

        // Create a new HashSet populated with even numbers.
        HashSet<int> numbers = new HashSet<int>(evenNumbers);
        Console.WriteLine("numbers UnionWith oddNumbers...");
        numbers.UnionWith(oddNumbers);

        Console.Write("numbers contains {0} elements: ", numbers.Count);
        DisplaySet(numbers);

    }

    private static void DisplaySet(HashSet<int> set)
    {
        Console.Write("{");
        foreach (int i in set)
        {
            Console.Write(" {0}", i);
        }
        Console.WriteLine(" }");
    }
}
/* This example produces output similar to the following:
 * evenNumbers contains 5 elements: { 0 2 4 6 8 }
 * oddNumbers contains 5 elements: { 1 3 5 7 9 }
 * numbers UnionWith oddNumbers...
 * numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }
 */

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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