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).
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.Booleantrue 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).| Exception | Condition |
|---|---|
| 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
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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.