Enumerable.Except メソッド

定義

2 つのシーケンスの差集合を生成します。Produces the set difference of two sequences.

オーバーロード

Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

既定の等値比較子を使用して値を比較することにより、2 つのシーケンスの差集合を生成します。Produces the set difference of two sequences by using the default equality comparer to compare values.

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

指定された IEqualityComparer<T> を使用して値を比較することにより、2 つのシーケンスの差集合を生成します。Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.

注釈

2つのセットの差集合は、2番目のセットには表示されない1番目のセットのメンバーとして定義されます。The set difference of two sets is defined as the members of the first set that don't appear in the second set.

このメソッドは、secondに表示されない first 内の要素を返します。This method returns those elements in first that don't appear in second. firstに表示されない second の要素は返しません。It doesn't return those elements in second that don't appear in first. 一意の要素のみが返されます。Only unique elements are returned.

Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

既定の等値比較子を使用して値を比較することにより、2 つのシーケンスの差集合を生成します。Produces the set difference of two sequences by using the default equality comparer to compare values.

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

型パラメーター

TSource

入力シーケンスの要素の型。The type of the elements of the input sequences.

パラメーター

first
IEnumerable<TSource>

second には含まれていないが、返される要素を含む IEnumerable<T>An IEnumerable<T> whose elements that are not also in second will be returned.

second
IEnumerable<TSource>

最初のシーケンスにも含まれ、返されたシーケンスからは削除される要素を含む IEnumerable<T>An IEnumerable<T> whose elements that also occur in the first sequence will cause those elements to be removed from the returned sequence.

戻り値

IEnumerable<TSource>

2 つのシーケンスの要素の差集合が格納されているシーケンス。A sequence that contains the set difference of the elements of two sequences.

例外

first または secondnull です。first or second is null.

次のコード例は、Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) メソッドを使用して、2つの数値のシーケンスを比較し、最初のシーケンスにのみ出現する要素を返す方法を示しています。The following code example demonstrates how to use the Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method to compare two sequences of numbers and return elements that appear only in the first sequence.

double[] numbers1 = { 2.0, 2.0, 2.1, 2.2, 2.3, 2.3, 2.4, 2.5 };
double[] numbers2 = { 2.2 };

IEnumerable<double> onlyInFirstSet = numbers1.Except(numbers2);

foreach (double number in onlyInFirstSet)
    Console.WriteLine(number);

/*
 This code produces the following output:

 2
 2.1
 2.3
 2.4
 2.5
*/
' Create two arrays of doubles.
Dim numbers1() As Double = { 2.0, 2.0, 2.1, 2.2, 2.3, 2.3, 2.4, 2.5 }
Dim numbers2() As Double = {2.2}

' Select the elements from the first array that are not
' in the second array.
Dim onlyInFirstSet As IEnumerable(Of Double) = numbers1.Except(numbers2)

Dim output As New System.Text.StringBuilder
For Each number As Double In onlyInFirstSet
    output.AppendLine(number)
Next

' Display the output.
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' 2
' 2.1
' 2.3
' 2.4
' 2.5

一部のカスタムデータ型のオブジェクトのシーケンスを比較する場合は、IEquatable<T> ジェネリックインターフェイスをヘルパークラスに実装する必要があります。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. 次のコード例は、カスタムデータ型にこのインターフェイスを実装し、GetHashCode および Equals メソッドをオーバーライドする方法を示しています。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

このインターフェイスを実装した後、次の例に示すように、Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) メソッドで ProductA オブジェクトのシーケンスを使用できます。After you implement this interface, you can use sequences of ProductA objects in the Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method, as shown in the following example:

ProductA[] fruits1 = { new ProductA { Name = "apple", Code = 9 }, 
                       new ProductA { Name = "orange", Code = 4 },
                        new ProductA { Name = "lemon", Code = 12 } };

ProductA[] fruits2 = { new ProductA { Name = "apple", Code = 9 } };

//Get all the elements from the first array
//except for the elements from the second array.

IEnumerable<ProductA> except =
    fruits1.Except(fruits2);

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

/*
  This code produces the following output:
 
  orange 4
  lemon 12
*/
Dim fruits1() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}, 
     New Product With {.Name = "lemon", .Code = 12}}

Dim fruits2() As Product = 
    {New Product With {.Name = "apple", .Code = 9}}

' Get all the elements from the first array
' except for the elements from the second array.

Dim except = fruits1.Except(fruits2)

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

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

注釈

このメソッドは、遅延実行を使用して実装されます。This method is implemented by using deferred execution. イミディエイトの戻り値は、アクションを実行するために必要なすべての情報を格納するオブジェクトです。The immediate return value is an object that stores all the information that is required to perform the action. か、呼び出すことによって、オブジェクトが列挙されるまで、このメソッドによって表されるクエリは実行されません、GetEnumeratorメソッドを使用して直接またはforeachVisual C# またはFor EachVisual Basic で。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.

既定の等値比較子である Defaultは、型の値を比較するために使用されます。The default equality comparer, Default, is used to compare values of the types. カスタムデータ型を比較するには、EqualsGetHashCode メソッドをオーバーライドし、必要に応じてカスタム型の IEquatable<T> ジェネリックインターフェイスを実装する必要があります。To compare a custom data type, you need to override the Equals and the GetHashCode methods, and optionally implement the IEquatable<T> generic interface in the custom type. 詳細については、Default プロパティを参照してください。For more information, see the Default property.

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

指定された IEqualityComparer<T> を使用して値を比較することにより、2 つのシーケンスの差集合を生成します。Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.

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

型パラメーター

TSource

入力シーケンスの要素の型。The type of the elements of the input sequences.

パラメーター

first
IEnumerable<TSource>

second には含まれていないが、返される要素を含む IEnumerable<T>An IEnumerable<T> whose elements that are not also in second will be returned.

second
IEnumerable<TSource>

最初のシーケンスにも含まれ、返されたシーケンスからは削除される要素を含む IEnumerable<T>An IEnumerable<T> whose elements that also occur in the first sequence will cause those elements to be removed from the returned sequence.

comparer
IEqualityComparer<TSource>

値を比較する IEqualityComparer<T>An IEqualityComparer<T> to compare values.

戻り値

IEnumerable<TSource>

2 つのシーケンスの要素の差集合が格納されているシーケンス。A sequence that contains the set difference of the elements of two sequences.

例外

first または secondnull です。first or second is null.

一部のカスタムデータ型のオブジェクトのシーケンスを比較する場合は、IEqualityComparer<T> ジェネリックインターフェイスをヘルパークラスに実装する必要があります。If you want to compare sequences of objects of some custom data type, you have to implement the IEqualityComparer<T> generic interface in a helper class. 次のコード例は、カスタムデータ型にこのインターフェイスを実装し、GetHashCode メソッドと Equals メソッドを提供する方法を示しています。The following code example shows how to implement this interface in a custom data type and provide GetHashCode and Equals methods. 次の例は、Except メソッドで使用できる等値比較子を実装する方法を示しています。The following example shows how to implement an equality comparer that can be used in the Except 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

この比較子を実装した後、次の例に示すように、Except メソッドで Product オブジェクトのシーケンスを使用できます。After you implement this comparer, you can use sequences of Product objects in the Except method, as shown in the following example:

Product[] fruits1 = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "orange", Code = 4 },
                        new Product { Name = "lemon", Code = 12 } };

Product[] fruits2 = { new Product { Name = "apple", Code = 9 } };

//Get all the elements from the first array
//except for the elements from the second array.

IEnumerable<Product> except =
    fruits1.Except(fruits2, new ProductComparer());

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

/*
  This code produces the following output:
 
  orange 4
  lemon 12
*/

Dim fruits1() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}, 
     New Product With {.Name = "lemon", .Code = 12}}

Dim fruits2() As Product = 
    {New Product With {.Name = "apple", .Code = 9}}

' Get all the elements from the first array
' except for the elements from the second array.

Dim except = fruits1.Except(fruits2, New ProductComparer())

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

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

注釈

comparernull場合、既定の等値比較子である Defaultが、値の比較に使用されます。If comparer is null, the default equality comparer, Default, is used to compare values.

適用対象