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HashSet<T>.Contains Method

Determines whether a HashSet<T> object contains the specified element.

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

public bool Contains(
	T item
)

Parameters

item
Type: T

The element to locate in the HashSet<T> object.

Return Value

Type: System.Boolean
true if the HashSet<T> object contains the specified element; otherwise, false.

Implements

ICollection<T>.Contains(T)

This method is an O(1) operation.

The following example demonstrates how to remove values from a HashSet<T> collection using the Remove method. In this example, the Contains method verifies that the set contains a value before removing it.

    static void Main()
    {
        HashSet<int> evenNumbers = new HashSet<int>();

        for (int i = 0; i < 20; i++)
        {
            evenNumbers.Add(i);
        }

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

        evenNumbers.RemoveWhere(isEven);

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

        if (evenNumbers.Contains(0))
        {
            evenNumbers.Remove(0);
        }

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

    private static bool isEven(int i)
    {
        return ((i % 2) == 1);
    }
/* This example produces output similar to the following:
 * evenNumbers contains 20 elements: { 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 }
 * evenNumbers contains 10 elements: { 0 2 4 6 8 10 12 14 16 18 }
 * evenNumbers contains 9 elements: { 2 4 6 8 10 12 14 16 18 }
 */

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

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

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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