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Enumerable.SequenceEqual(Of TSource) Method (IEnumerable(Of TSource), IEnumerable(Of TSource), IEqualityComparer(Of TSource))

 

Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer(Of T).

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

<ExtensionAttribute>
Public Shared Function SequenceEqual(Of TSource) (
	first As IEnumerable(Of TSource),
	second As IEnumerable(Of TSource),
	comparer As IEqualityComparer(Of TSource)
) As Boolean

Parameters

first
Type: System.Collections.Generic.IEnumerable(Of TSource)

An IEnumerable(Of T) to compare to second.

second
Type: System.Collections.Generic.IEnumerable(Of TSource)

An IEnumerable(Of T) to compare to the first sequence.

comparer
Type: System.Collections.Generic.IEqualityComparer(Of TSource)

An IEqualityComparer(Of T) to use to compare elements.

Return Value

Type: System.Boolean

true if the two source sequences are of equal length and their corresponding elements compare equal according to comparer; otherwise, false.

Type Parameters

TSource

The type of the elements of the input sequences.

Exception Condition
ArgumentNullException

first or second is null.

The SequenceEqual(Of TSource)(IEnumerable(Of TSource), IEnumerable(Of TSource), IEqualityComparer(Of TSource)) method enumerates the two source sequences in parallel and compares corresponding elements by using the specified IEqualityComparer(Of T). If comparer is null, the default equality comparer, Default, is used to compare elements.

The following example shows how to implement an equality comparer that can be used in the SequenceEqual(Of TSource)(IEnumerable(Of TSource), IEnumerable(Of TSource), IEqualityComparer(Of TSource)) method.

Public Class Product
    Public Property Name As String
    Public Property Code As Integer
End Class

' Custom comparer for the Product class
Public Class ProductComparer
    Implements IEqualityComparer(Of Product)

    Public Function Equals1(
        ByVal x As Product, 
        ByVal y As Product
        ) As Boolean Implements IEqualityComparer(Of Product).Equals

        ' Check whether the compared objects reference the same data.
        If x Is y Then Return True

        'Check whether any of the compared objects is null.
        If x Is Nothing OrElse y Is Nothing Then Return False

        ' Check whether the products' properties are equal.
        Return (x.Code = y.Code) AndAlso (x.Name = y.Name)
    End Function

    Public Function GetHashCode1(
        ByVal product As Product
        ) As Integer Implements IEqualityComparer(Of Product).GetHashCode

        ' Check whether the object is null.
        If product Is Nothing Then Return 0

        ' Get hash code for the Name field if it is not null.
        Dim hashProductName = 
            If(product.Name Is Nothing, 0, product.Name.GetHashCode())

        ' Get hash code for the Code field.
        Dim hashProductCode = product.Code.GetHashCode()

        ' Calculate the hash code for the product.
        Return hashProductName Xor hashProductCode
    End Function
End Class

After you implement this comparer, you can use sequences of Product objects in the SequenceEqual(Of TSource)(IEnumerable(Of TSource), IEnumerable(Of TSource), IEqualityComparer(Of TSource)) method, as shown in the following example.


Dim storeA() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}}

Dim storeB() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}}

Dim equalAB = storeA.SequenceEqual(storeB, New ProductComparer())

Console.WriteLine("Equal? " & equalAB)

' This code produces the following output:

' Equal? True

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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