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HashSet<T>.Overlaps Method

Determines whether the current HashSet<T> object and a specified collection share common elements.

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

public bool Overlaps(
	IEnumerable<T> other
)

Parameters

other
Type: System.Collections.Generic.IEnumerable<T>

The collection to compare to the current HashSet<T> object.

Return Value

Type: System.Boolean
true if the HashSet<T> object and other share at least one common element; otherwise, false.

Implements

ISet<T>.Overlaps(IEnumerable<T>)

ExceptionCondition
ArgumentNullException

other is null.

This method is an O(n) operation, where n is the number of elements in other.

The following example creates two disparate HashSet<T> objects and compares them to each another. In this example, allNumbers and lowNumbers are shown to share common elements using the Overlaps method.

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

    for (int i = 1; i < 5; i++)
    {
        lowNumbers.Add(i);
    }

    for (int i = 0; i < 10; i++)
    {
        allNumbers.Add(i);
    }

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

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

    Console.WriteLine("lowNumbers overlaps allNumbers: {0}",
        lowNumbers.Overlaps(allNumbers));

    Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}",
        allNumbers.SetEquals(lowNumbers));

    // Show the results of sub/superset testing
    Console.WriteLine("lowNumbers is a subset of allNumbers: {0}",
        lowNumbers.IsSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a superset of lowNumbers: {0}",
        allNumbers.IsSupersetOf(lowNumbers));
    Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}",
        lowNumbers.IsProperSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}",
        allNumbers.IsProperSupersetOf(lowNumbers));

    // Modify allNumbers to remove numbers that are not in lowNumbers.
    allNumbers.IntersectWith(lowNumbers);
    Console.Write("allNumbers contains {0} elements: ", allNumbers.Count);
    DisplaySet(allNumbers);

    Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}",
        allNumbers.SetEquals(lowNumbers));

    // Show the results of sub/superset testing with the modified set.
    Console.WriteLine("lowNumbers is a subset of allNumbers: {0}",
        lowNumbers.IsSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a superset of lowNumbers: {0}",
        allNumbers.IsSupersetOf(lowNumbers));
    Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}",
        lowNumbers.IsProperSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}",
        allNumbers.IsProperSupersetOf(lowNumbers));
}
/* This code example produces output similar to the following:
 * lowNumbers contains 4 elements: { 1 2 3 4 }
 * allNumbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
 * lowNumbers overlaps allNumbers: True
 * allNumbers and lowNumbers are equal sets: False
 * lowNumbers is a subset of allNumbers: True
 * allNumbers is a superset of lowNumbers: True
 * lowNumbers is a proper subset of allNumbers: True
 * allNumbers is a proper superset of lowNumbers: True
 * allNumbers contains 4 elements: { 1 2 3 4 }
 * allNumbers and lowNumbers are equal sets: True
 * lowNumbers is a subset of allNumbers: True
 * allNumbers is a superset of lowNumbers: True
 * lowNumbers is a proper subset of allNumbers: False
 * allNumbers is a proper superset of lowNumbers: False
 */

.NET Framework

Supported in: 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 Silverlight 8.1, Windows Phone Silverlight 8

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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