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

Reference

Definition

Namespace:: System.Collections.Generic

Assembly:: System.Collections.dll

Assembly:: System.Core.dll

Assembly:: netstandard.dll

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

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

public:
 virtual bool Overlaps(System::Collections::Generic::IEnumerable<T> ^ other);

public:
 bool Overlaps(System::Collections::Generic::IEnumerable<T> ^ other);

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

abstract member Overlaps : seq<'T> -> bool
override this.Overlaps : seq<'T> -> bool

member this.Overlaps : seq<'T> -> bool

Public Function Overlaps (other As IEnumerable(Of T)) As Boolean

Parameters

other: IEnumerable<T>

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

Returns

Boolean

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

Implements

Overlaps(IEnumerable<T>) Overlaps(IEnumerable<T>)

Exceptions

ArgumentNullException

other is null.

Examples

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.

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
*/

let displaySet (set: HashSet<int>) =
    printf "{"

    for i in set do
        printf $" {i}"

    printfn " }"

let lowNumbers = HashSet<int>()
let allNumbers = HashSet<int>()

for i = 1 to 4 do
    lowNumbers.Add i |> ignore


for i = 0 to 9 do
    allNumbers.Add i |> ignore

printf $"lowNumbers contains {lowNumbers.Count} elements: "
displaySet lowNumbers

printf $"allNumbers contains {allNumbers.Count} elements: "
displaySet allNumbers

printfn $"lowNumbers overlaps allNumbers: {lowNumbers.Overlaps allNumbers}"

printfn $"allNumbers and lowNumbers are equal sets: {allNumbers.SetEquals lowNumbers}"

// Show the results of sub/superset testing
printfn $"lowNumbers is a subset of allNumbers: {lowNumbers.IsSubsetOf allNumbers}"
printfn $"allNumbers is a superset of lowNumbers: {allNumbers.IsSupersetOf lowNumbers}"
printfn $"lowNumbers is a proper subset of allNumbers: {lowNumbers.IsProperSubsetOf allNumbers}"
printfn $"allNumbers is a proper superset of lowNumbers: {allNumbers.IsProperSupersetOf lowNumbers}"

// Modify allNumbers to remove numbers that are not in lowNumbers.
allNumbers.IntersectWith lowNumbers
printf $"allNumbers contains {allNumbers.Count} elements: "
displaySet allNumbers

printfn $"allNumbers and lowNumbers are equal sets: {allNumbers.SetEquals lowNumbers}"

// Show the results of sub/superset testing with the modified set.
printfn $"lowNumbers is a subset of allNumbers: {lowNumbers.IsSubsetOf allNumbers}"
printfn $"allNumbers is a superset of lowNumbers: {allNumbers.IsSupersetOf lowNumbers}"
printfn $"lowNumbers is a proper subset of allNumbers: {lowNumbers.IsProperSubsetOf allNumbers}"
printfn $"allNumbers is a proper superset of lowNumbers: {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

Shared Sub Main()

    Dim lowNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
    Dim allNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

    For i As Integer = 1 To 4
        lowNumbers.Add(i)
    Next i

    For i As Integer = 0 To 9
        allNumbers.Add(i)
    Next 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))
End Sub
' 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

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

Applies to

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