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HashSet<T>.RemoveWhere Method

Removes all elements that match the conditions defined by the specified predicate from a HashSet<T> collection.

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

public int RemoveWhere(
	Predicate<T> match
)

Parameters

match
Type: System.Predicate<T>

The Predicate<T> delegate that defines the conditions of the elements to remove.

Return Value

Type: System.Int32
The number of elements that were removed from the HashSet<T> collection.

ExceptionCondition
ArgumentNullException

match is null.

Calling this method is an O(n) operation, where n is Count.

The following example demonstrates how to remove values from a HashSet<T> collection using the Remove method. In this example, all odd integers are removed from the HashSet<T> collection as specified by the match delegate.

    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: 4.6, 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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