SequenceEqual(TSource) Method (IEnumerable(TSource), IEnumerable(TSource), IEqualityComparer(TSource))

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

Updated: October 2008

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)

'Declaration
<ExtensionAttribute> _
Public Shared Function SequenceEqual(Of TSource) ( _
	first As IEnumerable(Of TSource), _
	second As IEnumerable(Of TSource), _
	comparer As IEqualityComparer(Of TSource) _
) As Boolean
'Usage
Dim first As IEnumerable(Of TSource)
Dim second As IEnumerable(Of TSource)
Dim comparer As IEqualityComparer(Of TSource)
Dim returnValue As Boolean 

returnValue = first.SequenceEqual(second, _
	comparer)

Type Parameters

TSource

The type of the elements of the input sequences.

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.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of TSource). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
ArgumentNullException

first or second is Nothing.

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

        ' Get the 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

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0

Date

History

Reason

October 2008

Added an example.

Customer feedback.

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