Enumerable.SequenceEqual 方法

定义

根据相等比较器确定两个序列是否相等。

重载

SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

通过使用相应类型的默认相等比较器对序列的元素进行比较,以确定两个序列是否相等。

SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

通过使用指定的 IEqualityComparer<T> 来比较两个序列的元素,以确定这两个序列是否相等。

SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

通过使用相应类型的默认相等比较器对序列的元素进行比较,以确定两个序列是否相等。

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool SequenceEqual(System::Collections::Generic::IEnumerable<TSource> ^ first, System::Collections::Generic::IEnumerable<TSource> ^ second);
public static bool SequenceEqual<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second);
static member SequenceEqual : seq<'Source> * seq<'Source> -> bool
<Extension()>
Public Function SequenceEqual(Of TSource) (first As IEnumerable(Of TSource), second As IEnumerable(Of TSource)) As Boolean

类型参数

TSource

输入序列中的元素的类型。

参数

first
IEnumerable<TSource>

一个用于比较 secondIEnumerable<T>

second
IEnumerable<TSource>

要与第一个序列进行比较的 IEnumerable<T>

返回

Boolean

如果根据相应类型的默认相等比较器,两个源序列的长度相等,且其相应元素相等,则为 true;否则为 false

例外

firstsecondnull

示例

下面的代码示例演示如何用于 SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) 确定两个序列是否相等。 在前两个示例中,该方法确定比较序列是否包含对相同对象的引用。 在第三个和第四个示例中,该方法比较序列中对象的实际数据。

在此示例中,序列相等。

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void SequenceEqualEx1()
{
    Pet pet1 = new Pet { Name = "Turbo", Age = 2 };
    Pet pet2 = new Pet { Name = "Peanut", Age = 8 };

    // Create two lists of pets.
    List<Pet> pets1 = new List<Pet> { pet1, pet2 };
    List<Pet> pets2 = new List<Pet> { pet1, pet2 };

    bool equal = pets1.SequenceEqual(pets2);

    Console.WriteLine(
        "The lists {0} equal.",
        equal ? "are" : "are not");
}

/*
 This code produces the following output:

 The lists are equal.
*/
Class Pet
    Public Name As String
    Public Age As Integer
End Class

Sub SequenceEqualEx1()
    ' Create two Pet objects.
    Dim pet1 As New Pet With {.Name = "Turbo", .Age = 2}
    Dim pet2 As New Pet With {.Name = "Peanut", .Age = 8}

    ' Create two lists of pets.
    Dim pets1 As New List(Of Pet)(New Pet() {pet1, pet2})
    Dim pets2 As New List(Of Pet)(New Pet() {pet1, pet2})

    'Determine if the two lists are equal.
    Dim equal As Boolean = pets1.SequenceEqual(pets2)

    ' Display the output.
    Dim text As String = IIf(equal, "are", "are not")
    Console.WriteLine($"The lists {text} equal.")

End Sub

' This code produces the following output:
'
' The lists are equal.

下面的代码示例比较了两个不相等的序列。 请注意,序列包含相同的数据,但由于它们包含的对象具有不同的引用,因此序列不被视为相等。

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void SequenceEqualEx2()
{
    Pet pet1 = new Pet() { Name = "Turbo", Age = 2 };
    Pet pet2 = new Pet() { Name = "Peanut", Age = 8 };

    // Create two lists of pets.
    List<Pet> pets1 = new List<Pet> { pet1, pet2 };
    List<Pet> pets2 =
        new List<Pet> { new Pet { Name = "Turbo", Age = 2 },
                        new Pet { Name = "Peanut", Age = 8 } };

    bool equal = pets1.SequenceEqual(pets2);

    Console.WriteLine("The lists {0} equal.", equal ? "are" : "are not");
}

/*
 This code produces the following output:

 The lists are not equal.
*/
' Create two Pet objects.
Dim pet1 As New Pet With {.Name = "Turbo", .Age = 2}
Dim pet2 As New Pet With {.Name = "Peanut", .Age = 8}

' Create two lists of pets.
Dim pets1 As New List(Of Pet)()
pets1.Add(pet1)
pets1.Add(pet2)

Dim pets2 As New List(Of Pet)()
pets2.Add(New Pet With {.Name = "Turbo", .Age = 2})
pets2.Add(New Pet With {.Name = "Peanut", .Age = 8})

' Determine if the two lists are equal.
Dim equal As Boolean = pets1.SequenceEqual(pets2)

' Display the output.
Dim text As String = IIf(equal, "are", "are not")
Console.WriteLine($"The lists {text} equal.")

' This code produces the following output:
'
' The lists are not equal.

如果要比较序列中对象的实际数据,而不是只是比较其引用,则必须在类中实现 IEqualityComparer<T> 泛型接口。 下面的代码示例演示如何在帮助程序类中实现此接口并提供 GetHashCodeEquals 方法。

public class ProductA : IEquatable<ProductA>
{
    public string Name { get; set; }
    public int Code { get; set; }

    public bool Equals(ProductA other)
    {
        if (other is null)
            return false;

        return this.Name == other.Name && this.Code == other.Code;
    }

    public override bool Equals(object obj) => Equals(obj as ProductA);
    public override int GetHashCode() => (Name, Code).GetHashCode();
}
Public Class ProductA
    Inherits IEquatable(Of ProductA)

    Public Property Name As String
    Public Property Code As Integer

    Public Function Equals(ByVal other As ProductA) As Boolean
        If other Is Nothing Then Return False
        Return Me.Name = other.Name AndAlso Me.Code = other.Code
    End Function

    Public Overrides Function Equals(ByVal obj As Object) As Boolean
        Return Equals(TryCast(obj, ProductA))
    End Function

    Public Overrides Function GetHashCode() As Integer
        Return (Name, Code).GetHashCode()
    End Function

End Class

实现此接口后,可以在方法中使用SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)对象序列ProductA,如以下示例所示:


ProductA[] storeA = { new ProductA { Name = "apple", Code = 9 },
                       new ProductA { Name = "orange", Code = 4 } };

ProductA[] storeB = { new ProductA { Name = "apple", Code = 9 },
                       new ProductA { Name = "orange", Code = 4 } };

bool equalAB = storeA.SequenceEqual(storeB);

Console.WriteLine("Equal? " + equalAB);

/*
    This code produces the following output:

    Equal? True
*/
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)

Console.WriteLine("Equal? " & equalAB)

' This code produces the following output:

' Equal? True

注解

该方法SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)并行枚举两个源序列,并使用默认的相等比较器比较TSourceDefault相应的元素。

默认相等比较器 Default用于比较类型的值。 若要比较自定义数据类型,需要重写 EqualsGetHashCode 方法,并选择性地在自定义类型中实现 IEquatable<T> 泛型接口。 有关更多信息,请参见 Default 属性。

适用于

SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

通过使用指定的 IEqualityComparer<T> 来比较两个序列的元素,以确定这两个序列是否相等。

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool SequenceEqual(System::Collections::Generic::IEnumerable<TSource> ^ first, System::Collections::Generic::IEnumerable<TSource> ^ second, System::Collections::Generic::IEqualityComparer<TSource> ^ comparer);
public static bool SequenceEqual<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second, System.Collections.Generic.IEqualityComparer<TSource> comparer);
public static bool SequenceEqual<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second, System.Collections.Generic.IEqualityComparer<TSource>? comparer);
static member SequenceEqual : seq<'Source> * seq<'Source> * System.Collections.Generic.IEqualityComparer<'Source> -> bool
<Extension()>
Public Function SequenceEqual(Of TSource) (first As IEnumerable(Of TSource), second As IEnumerable(Of TSource), comparer As IEqualityComparer(Of TSource)) As Boolean

类型参数

TSource

输入序列中的元素的类型。

参数

first
IEnumerable<TSource>

一个用于比较 secondIEnumerable<T>

second
IEnumerable<TSource>

要与第一个序列进行比较的 IEnumerable<T>

comparer
IEqualityComparer<TSource>

用于比较元素的 IEqualityComparer<T>

返回

Boolean

如果根据 comparer,两个源序列的长度相等,且其相应元素相等,则为 true;否则为 false

例外

firstsecondnull

示例

以下示例演示如何实现方法中使用的 SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) 相等比较器。

public class Product
{
    public string Name { get; set; }
    public int Code { get; set; }
}

// Custom comparer for the Product class
class ProductComparer : IEqualityComparer<Product>
{
    // Products are equal if their names and product numbers are equal.
    public bool Equals(Product x, Product y)
    {

        //Check whether the compared objects reference the same data.
        if (Object.ReferenceEquals(x, y)) return true;

        //Check whether any of the compared objects is null.
        if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
            return false;

        //Check whether the products' properties are equal.
        return x.Code == y.Code && x.Name == y.Name;
    }

    // If Equals() returns true for a pair of objects
    // then GetHashCode() must return the same value for these objects.

    public int GetHashCode(Product product)
    {
        //Check whether the object is null
        if (Object.ReferenceEquals(product, null)) return 0;

        //Get hash code for the Name field if it is not null.
        int hashProductName = product.Name == null ? 0 : product.Name.GetHashCode();

        //Get hash code for the Code field.
        int hashProductCode = product.Code.GetHashCode();

        //Calculate the hash code for the product.
        return hashProductName ^ hashProductCode;
    }
}
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

实现此比较器后,可以在方法中使用SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)对象的序列Product,如以下示例所示:


Product[] storeA = { new Product { Name = "apple", Code = 9 },
                       new Product { Name = "orange", Code = 4 } };

Product[] storeB = { new Product { Name = "apple", Code = 9 },
                       new Product { Name = "orange", Code = 4 } };

bool equalAB = storeA.SequenceEqual(storeB, new ProductComparer());

Console.WriteLine("Equal? " + equalAB);

/*
    This code produces the following output:

    Equal? True
*/

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

注解

该方法 SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) 并行枚举两个源序列,并使用指定的 IEqualityComparer<T>元素比较相应的元素。 如果comparernullDefault,则使用默认相等比较器比较元素。

适用于