Enumerable.Union 方法

參考

定義

命名空間:: System.Linq

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等位。

多載

Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	使用預設相等比較值來比較值，以便產生兩個序列的集合等位。
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	使用指定的 IEqualityComparer<T> 產生兩個序列的集合等位。

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

來源:: Union.cs

來源:: Union.cs

來源:: Union.cs

使用預設相等比較值來比較值，以便產生兩個序列的集合等位。

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

輸入序列之項目的類型。

參數

first: IEnumerable<TSource>

IEnumerable<T>，其獨特項目構成第一個等位集合。

second: IEnumerable<TSource>

IEnumerable<T>，其獨特項目構成第二個等位集合。

傳回

IEnumerable<TSource>

IEnumerable<T>，其中包含來自兩個輸入序列的項目，但不包括重複的項目。

例外狀況

ArgumentNullException

first 或 second 為 null。

範例

下列程式代碼範例示範如何使用 Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) 來取得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

如果您想要比較某些自定義數據類型的物件序列，則必須在協助程序類別中實 IEquatable<T> 作泛型介面。下列程式代碼範例示範如何在自定義數據類型中實作這個介面，並覆寫 GetHashCode 和 Equals 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

實作此介面之後，您可以在方法中使用Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)物件序列ProductA，如下列範例所示：

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

這個方法是使用延後執行來實作。立即傳回值是一個物件，會儲存執行動作所需的所有資訊。除非直接呼叫其 GetEnumerator 方法或在 C# 或 foreachFor Each Visual Basic 中使用來列舉對象，否則不會執行這個方法所代表的查詢。

這個方法會從傳回集排除重複專案。這個行為與 Concat 方法不同，它會傳回輸入序列中的所有專案，包括重複專案。

默認的相等比較子 Default是用來比較實 IEqualityComparer<T> 作泛型介面之型別的值。若要比較自定義數據類型，您必須實作此介面，並提供您自己的 GetHashCode 和 Equals 方法給類型。

列舉這個方法所傳回的物件時， Union 會 first 依該順序列舉和 second ，併產生尚未產生的每個專案。

適用於

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

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等位。

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

輸入序列之項目的類型。

參數

first: IEnumerable<TSource>

IEnumerable<T>，其獨特項目構成第一個等位集合。

second: IEnumerable<TSource>

IEnumerable<T>，其獨特項目構成第二個等位集合。

comparer: IEqualityComparer<TSource>

用來比較值的 IEqualityComparer<T>。

傳回

IEnumerable<TSource>

IEnumerable<T>，其中包含來自兩個輸入序列的項目，但不包括重複的項目。

例外狀況

ArgumentNullException

first 或 second 為 null。

範例

下列範例示範如何實作可用於方法的 Union 相等比較子。

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

實作這個比較子之後，您可以在方法中使用Union物件序列Product，如下列範例所示：

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

如果為 comparernull，則會使用預設相等比較子 Default來比較值。

列舉這個方法所傳回的物件時， Union 會 first 依該順序列舉和 second ，併產生尚未產生的每個專案。

方法 Concat 與方法不同 Union ， Concat 因為方法會傳回輸入序列中的所有專案，包括重複專案，而 Union 只會傳回唯一值。

適用於

共用方式為

Enumerable.Union 方法

定義

多載

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

其他資源