Enumerable.Union 方法

定義

命名空間:: System.Linq

組件:: System.Core.dll, System.Linq.dll

組件:: netstandard.dll, System.Linq.dll

組件:: System.Linq.dll

組件:: System.Core.dll

組件:: netstandard.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

產生兩個序列的集合聯集。

多載

名稱	Description
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	使用預設相等比較子產生兩個序列的集合聯集。
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	使用指定的 IEqualityComparer<T>產生兩個序列的集合聯集。

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

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

使用預設相等比較子產生兩個序列的集合聯集。

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)

類型參數

TSource

輸入序列元素的類型。

參數

first: IEnumerable<TSource>

一個 IEnumerable<T> 其不同元素組成聯集的第一集合。

second: IEnumerable<TSource>

一個 IEnumerable<T> 其不同元素組成聯集的第二集合。

傳回

IEnumerable<TSource>

包含 IEnumerable<T> 兩個輸入序列元素（排除重複序列）的。

例外狀況

ArgumentNullException

first 或 second 為 null。

範例

以下程式碼範例示範如何取得 Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) 兩個整數序列的聯集。

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
Console.WriteLine(output.ToString())

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

如果你想比較某個自訂資料型態的物件序列，你必須在輔助類別中實作 IEquatable<T> 通用介面。以下程式碼範例展示了如何在自訂資料型態及覆寫GetHashCode Equals方法中實作此介面。

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

實作此介面後，你可以在方法中使用物件序列ProductAUnion<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)，如下範例所示：

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
'

備註

此方法透過延遲執行實現。立即回傳值是一個物件，儲存執行動作所需的所有資訊。此方法所代表的查詢，直到物件被枚舉，無論是直接呼叫其 GetEnumerator 方法，或是使用 C# 中的 foreach，或在 Visual Basic 中使用 For Each，才會執行。

此方法排除重複的返回集。這與 Concat 方法不同，該方法會回傳輸入序列中的所有元素，包括重複的元素。

預設的等式比較器 Default，用於比較實作 IEqualityComparer<T> 通用介面的各類型值。要比較自訂資料型別，你需要實作這個介面，並提供你自己的GetHashCode Equals方法。

當此方法回傳的物件被枚舉時，會 Union 依序枚舉 first 和 second ，並產生尚未被輸入的每個元素。

適用於

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

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

使用指定的 IEqualityComparer<T>產生兩個序列的集合聯集。

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);

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)

類型參數

TSource

輸入序列元素的類型。

參數

first: IEnumerable<TSource>

一個 IEnumerable<T> 其不同元素組成聯集的第一集合。

second: IEnumerable<TSource>

一個 IEnumerable<T> 其不同元素組成聯集的第二集合。

comparer: IEqualityComparer<TSource>

比較 IEqualityComparer<T> 價值。

傳回

IEnumerable<TSource>

包含 IEnumerable<T> 兩個輸入序列元素（排除重複序列）的。

例外狀況

ArgumentNullException

first 或 second 為 null。

範例

以下範例說明如何實作可用於該 Union 方法的等號比較器。

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

實作此比較器後，你可以在方法中使用物件Product序列Union，如下範例所示：

Product[] store10 = { new Product { Name = "apple", Code = 9 },
                       new Product { Name = "orange", Code = 4 } };

Product[] store20 = { new Product { Name = "apple", Code = 9 },
                       new Product { Name = "lemon", Code = 12 } };

//Get the products from the both arrays
//excluding duplicates.

IEnumerable<Product> union =
  store10.Union(store20, new ProductComparer());

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

/*
    This code produces the following output:

    apple 9
    orange 4
    lemon 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.

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
'

備註

若 comparer ， null則預設等式比較器 Default，用於比較數值。

當此方法回傳的物件被枚舉時，會 Union 依序枚舉 first 和 second ，並產生尚未被輸入的每個元素。

此 Concat 方法與 Method Union 不同，因為 Concat 該方法回傳輸入序列中的所有元素（包括重複元素），而 Union 回傳的唯一值。

另請參閱

UnionBy 方法

適用於

意見反應

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