Enumerable.Union 方法

定义

生成两个序列的并集。Produces the set union of two sequences.

重载

Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

通过使用默认的相等比较器,生成两个序列的并集。Produces the set union of two sequences by using the default equality comparer.

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

通过使用指定的 IEqualityComparer<T> 生成两个序列的并集。Produces the set union of two sequences by using a specified IEqualityComparer<T>.

注解

备注

本文中的一些 C# 示例在 Try.NET 内联代码运行程序和演练环境中运行。Some of the C# examples in this article run in the Try.NET inline code runner and playground. 选择“运行” 按钮(若有),在交互式窗口中运行示例。When present, select the Run button to run an example in an interactive window. 执行代码后,可通过再次选择“运行”来修改它并运行已修改的代码 。Once you execute the code, you can modify it and run the modified code by selecting Run again. 已修改的代码要么在交互窗口中运行,要么编译失败时,交互窗口将显示所有 C# 编译器错误消息。The modified code either runs in the interactive window or, if compilation fails, the interactive window displays all C# compiler error messages.

Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

通过使用默认的相等比较器,生成两个序列的并集。Produces the set union of two sequences by using the default equality comparer.

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

类型参数

TSource

输入序列中的元素的类型。The type of the elements of the input sequences.

参数

first
IEnumerable<TSource>

一个 IEnumerable<T>,其中的非重复元素构成并集的第一个部分。An IEnumerable<T> whose distinct elements form the first set for the union.

second
IEnumerable<TSource>

一个 IEnumerable<T>,其中的非重复元素构成并集的第二个部分。An IEnumerable<T> whose distinct elements form the second set for the union.

返回

IEnumerable<TSource>

一个 包含两个输入序列中的非重复元素的 IEnumerable<T>An IEnumerable<T> that contains the elements from both input sequences, excluding duplicates.

异常

firstsecondnullfirst or second is null.

示例

下面的代码示例演示如何使用 Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) 来获取两个整数序列的并集。The following code example demonstrates how to use Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) to obtain the union of two sequences of integers.

int[] ints1 = { 5, 3, 9, 7, 5, 9, 3, 7 };
int[] ints2 = { 8, 3, 6, 4, 4, 9, 1, 0 };

IEnumerable<int> union = ints1.Union(ints2);

foreach (int num in union)
{
    Console.Write("{0} ", num);
}

/*
 This code produces the following output:

 5 3 9 7 8 6 4 1 0
*/
' Create two arrays of integer values.
Dim ints1() As Integer = {5, 3, 9, 7, 5, 9, 3, 7}
Dim ints2() As Integer = {8, 3, 6, 4, 4, 9, 1, 0}

' Get the set union of the two arrays.
Dim union As IEnumerable(Of Integer) = ints1.Union(ints2)

' Display the resulting set's values.
Dim output As New System.Text.StringBuilder
For Each num As Integer In union
    output.AppendLine(num & " ")
Next
MsgBox(output.ToString())

' This code produces the following output:
'
' 5 
' 3 
' 9 
' 7 
' 8 
' 6 
' 4 
' 1 
' 0 

如果要比较某种自定义数据类型的对象序列,则必须在 helper 类中实现 IEquatable<T> 泛型接口。If you want to compare sequences of objects of some custom data type, you have to implement the IEquatable<T> generic interface in a helper class. 下面的代码示例演示如何在自定义数据类型中实现此接口,并覆盖 GetHashCode 和 @no__t 1 方法。The following code example shows how to implement this interface in a custom data type and override GetHashCode and Equals methods.

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,可以使用 Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) 方法中 @no__t 0 对象的序列,如以下示例中所示:After you implement this interface, you can use sequences of ProductA objects in the Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method, as shown in the following example:

ProductA[] store1 = { new ProductA { Name = "apple", Code = 9 }, 
                       new ProductA { Name = "orange", Code = 4 } };

ProductA[] store2 = { new ProductA { Name = "apple", Code = 9 }, 
                       new ProductA { Name = "lemon", Code = 12 } };
Dim store1() As ProductA = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}}

Dim store2() As ProductA = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "lemon", .Code = 12}}
//Get the products from the both arrays
//excluding duplicates.

IEnumerable<ProductA> union =
  store1.Union(store2);

foreach (var product in union)
    Console.WriteLine(product.Name + " " + product.Code);

/*
    This code produces the following output:
 
    apple 9
    orange 4
    lemon 12
*/
' Get the products from the both arrays
' excluding duplicates.

Dim union = store1.Union(store2)

For Each product In union
    Console.WriteLine(product.Name & " " & product.Code)
Next

' This code produces the following output:
'
' apple 9
' orange 4
' lemon 12
' 

注解

此方法是使用延迟执行实现的。This method is implemented by using deferred execution. 即时返回值是一个对象,该对象存储执行操作所需的所有信息。The immediate return value is an object that stores all the information that is required to perform the action. 在枚举对象之前,不会执行由此方法表示的查询,方法是:直接调用其 @no__t 0 方法,或者使用视觉C#对象中的 @no__t 或 @no__t Visual Basic 中的。The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

此方法排除返回集中的重复项。This method excludes duplicates from the return set. 这不同于 Concat 方法的行为,该方法返回输入序列中的所有元素,包括重复项。This is different behavior to the Concat method, which returns all the elements in the input sequences including duplicates.

默认的相等比较器 Default,用于比较实现 @no__t 泛型接口的类型的值。The default equality comparer, Default, is used to compare values of the types that implement the IEqualityComparer<T> generic interface. 若要比较自定义数据类型,需要实现此接口,并为该类型提供自己的 @no__t 0 和 @no__t 的方法。To compare a custom data type, you need to implement this interface and provide your own GetHashCode and Equals methods for the type.

枚举此方法返回的对象时,Union 按该顺序枚举 @no__t 和 @no__t,并生成尚未生成的每个元素。When the object returned by this method is enumerated, Union enumerates first and second in that order and yields each element that has not already been yielded.

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

通过使用指定的 IEqualityComparer<T> 生成两个序列的并集。Produces the set union of two sequences by using a specified IEqualityComparer<T>.

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

类型参数

TSource

输入序列中的元素的类型。The type of the elements of the input sequences.

参数

first
IEnumerable<TSource>

一个 IEnumerable<T>,其中的非重复元素构成并集的第一个部分。An IEnumerable<T> whose distinct elements form the first set for the union.

second
IEnumerable<TSource>

一个 IEnumerable<T>,其中的非重复元素构成并集的第二个部分。An IEnumerable<T> whose distinct elements form the second set for the union.

comparer
IEqualityComparer<TSource>

用于比较值的 IEqualityComparer<T>The IEqualityComparer<T> to compare values.

返回

IEnumerable<TSource>

一个 包含两个输入序列中的非重复元素的 IEnumerable<T>An IEnumerable<T> that contains the elements from both input sequences, excluding duplicates.

异常

firstsecondnullfirst or second is null.

示例

下面的示例演示如何实现可在 Union 方法中使用的相等比较器。The following example shows how to implement an equality comparer that can be used in the Union method.

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,可以使用 Union 方法中 @no__t 0 对象的序列,如以下示例中所示:After you implement this comparer, you can use sequences of Product objects in the Union method, as shown in the following example:

Product[] store1 = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "orange", Code = 4 } };

Product[] store2 = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "lemon", Code = 12 } };
Dim store1() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}}

Dim store2() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "lemon", .Code = 12}}
//Get the products from the both arrays
//excluding duplicates.

IEnumerable<Product> union =
  store1.Union(store2, new ProductComparer());

foreach (var product in union)
    Console.WriteLine(product.Name + " " + product.Code);

/*
    This code produces the following output:
 
    apple 9
    orange 4
    lemon 12
*/
' Get the products from the both arrays
' excluding duplicates.

Dim union = store1.Union(store2, New ProductComparer())

For Each product In union
    Console.WriteLine(product.Name & " " & product.Code)
Next

' This code produces the following output:
'
' apple 9
' orange 4
' lemon 12
' 

注解

此方法是使用延迟执行实现的。This method is implemented by using deferred execution. 即时返回值是一个对象,该对象存储执行操作所需的所有信息。The immediate return value is an object that stores all the information that is required to perform the action. 在枚举对象之前,不会执行由此方法表示的查询,方法是:直接调用其 @no__t 0 方法,或者使用视觉C#对象中的 @no__t 或 @no__t Visual Basic 中的。The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

如果 comparer @no__t 为-1,则使用默认的相等比较器 Default 来比较值。If comparer is null, the default equality comparer, Default, is used to compare values.

枚举此方法返回的对象时,Union 按该顺序枚举 @no__t 和 @no__t,并生成尚未生成的每个元素。When the object returned by this method is enumerated, Union enumerates first and second in that order and yields each element that has not already been yielded.

@No__t-0 方法不同于 Union 方法,因为 Concat 方法返回输入序列中的所有元素(包括重复项),而 Union 只返回唯一值。The Concat method differs from the Union method because the Concat method returns all the elements in the input sequences including duplicates, whereas Union returns only unique values.

适用于