HashSet<T>.SetEquals(IEnumerable<T>) Method

Definition

Namespace:

System.Collections.Generic

Assemblies:

netstandard.dll, System.Collections.dll

Source:

HashSet.cs

Determines whether a HashSet<T> object and the specified collection contain the same elements.

C#

public bool SetEquals(System.Collections.Generic.IEnumerable<T> other);

Parameters

other

IEnumerable<T>

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

Returns

Boolean

true if the HashSet<T> object is equal to other; otherwise, false.

Implements

SetEquals(IEnumerable<T>) SetEquals(IEnumerable<T>)

Exceptions

ArgumentNullException

other is null.

Examples

The following example creates two disparate HashSet<T> objects and compares them to each another. Initially, the two sets are not equal, which is demonstrated by using the SetEquals method. The allNumbers HashSet<T> object is then modified, after which the sets are equal.

C#

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));

void DisplaySet(HashSet<int> set)
{
    Console.Write("{");
    foreach (int i in set)
    {
        Console.Write(" {0}", i);
    }
    Console.WriteLine(" }");
}

/* 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
*/

Remarks

The SetEquals method ignores duplicate entries and the order of elements in the other parameter.

If the collection represented by other is a HashSet<T> collection with the same equality comparer as the current HashSet<T> object, this method is an O(n) operation. Otherwise, this method is an O(n + m) operation, where n is the number of elements in other and m is Count.

Applies to