Enumerable.Except Enumerable.Except Enumerable.Except Enumerable.Except Method

Definition

Erzeugt die Differenzmenge von zwei SequenzenProduces the set difference of two sequences.

Überlädt

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

Erzeugt die Differenzmenge zweier Sequenzen mithilfe des Standardgleichheitsvergleichs zum Vergleichen von WertenProduces the set difference of two sequences by using the default equality comparer to compare values.

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

Erzeugt mithilfe des angegebenen IEqualityComparer<T> die Differenzmenge zweier Sequenzen zum Vergleichen von WertenProduces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.

Hinweise

Die festgelegte Differenz von zwei Sätzen wird als die Member der ersten Menge definiert, die nicht in der zweiten Menge angezeigt werden.The set difference of two sets is defined as the members of the first set that don't appear in the second set.

Diese Methode gibt die Elemente in first zurück, die nicht secondin angezeigt werden.This method returns those elements in first that don't appear in second. Sie gibt nicht die Elemente in second zurück, die nicht firstin angezeigt werden.It doesn't return those elements in second that don't appear in first. Nur eindeutige Elemente werden zurückgegeben.Only unique elements are returned.

Hinweis

Einige der C#-Beispiele in diesem Artikel werden in der Inlinecodeausführung und dem Playground von Try.NET ausgeführt.Some of the C# examples in this article run in the Try.NET inline code runner and playground. Wenn vorhanden, klicken Sie auf die Schaltfläche Ausführen, um ein Beispiel in einem interaktiven Fenster auszuführen.When present, select the Run button to run an example in an interactive window. Nachdem Sie den Code ausgeführt haben, können Sie ihn ändern und den geänderten Code durch erneutes Anklicken der Schaltfläche Ausführen ausführen.Once you execute the code, you can modify it and run the modified code by selecting Run again. Der geänderte Code wird entweder im interaktiven Fenster ausgeführt, oder das interaktive Fenster zeigt alle C#-Compilerfehlermeldungen an, wenn die Kompilierung fehlschlägt.The modified code either runs in the interactive window or, if compilation fails, the interactive window displays all C# compiler error messages.

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

Erzeugt die Differenzmenge zweier Sequenzen mithilfe des Standardgleichheitsvergleichs zum Vergleichen von WertenProduces 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)

Typparameter

TSource

Der Typ der Elemente der Eingabesequenzen.The type of the elements of the input sequences.

Parameter

first
IEnumerable<TSource>

Es wird ein IEnumerable<T> zurückgegeben, dessen Elemente nicht auch in second enthalten sind.An IEnumerable<T> whose elements that are not also in second will be returned.

second
IEnumerable<TSource>

Wenn ein IEnumerable<T> Elemente enthält, die auch in der ersten Sequenz vorhanden sind, werden diese Elemente aus der zurückgegebenen Sequenz entfernt.An IEnumerable<T> whose elements that also occur in the first sequence will cause those elements to be removed from the returned sequence.

Gibt zurück

IEnumerable<TSource>

Eine Sequenz, die die Differenzmenge der Elemente von zwei Sequenzen enthält.A sequence that contains the set difference of the elements of two sequences.

Ausnahmen

first oder second ist null.first or second is null.

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie die Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) -Methode verwendet wird, um zwei Sequenzen von Zahlen zu vergleichen und um Elemente zurückzugeben, die nur in der ersten Sequenz angezeigt werden.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.
MsgBox(output.ToString())

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

Wenn Sie Sequenzen von Objekten eines benutzerdefinierten Datentyps vergleichen möchten, müssen Sie die IEquatable<T> generische-Schnittstelle in einer Hilfsklasse implementieren.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. Im folgenden Codebeispiel wird veranschaulicht, wie diese Schnittstelle in einem benutzerdefinierten Datentyp GetHashCode implementiert Equals und die-und-Methoden überschrieben werden.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

Nachdem Sie diese Schnittstelle implementiert haben, können Sie Sequenzen ProductA von Objekten in Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) der-Methode verwenden, wie im folgenden Beispiel gezeigt: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

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst GetEnumerator ausgeführt, wenn das Objekt durch Aufrufen der-Methode direkt oder mithilfe foreach von in Visual C# oder For Each Visual Basic aufgelistet wird.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.

Der Standard Gleichheits Vergleich, Default, wird verwendet, um Werte der Typen zu vergleichen.The default equality comparer, Default, is used to compare values of the types. Um einen benutzerdefinierten Datentyp zu vergleichen, müssen Sie die Equals -Methode GetHashCode und die-Methode überschreiben IEquatable<T> und optional die generische-Schnittstelle im benutzerdefinierten Typ implementieren.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. Weitere Informationen finden Sie in den Ausführungen zur Default-Eigenschaft.For more information, see the Default property.

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

Erzeugt mithilfe des angegebenen IEqualityComparer<T> die Differenzmenge zweier Sequenzen zum Vergleichen von WertenProduces 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)

Typparameter

TSource

Der Typ der Elemente der Eingabesequenzen.The type of the elements of the input sequences.

Parameter

first
IEnumerable<TSource>

Es wird ein IEnumerable<T> zurückgegeben, dessen Elemente nicht auch in second enthalten sind.An IEnumerable<T> whose elements that are not also in second will be returned.

second
IEnumerable<TSource>

Wenn ein IEnumerable<T> Elemente enthält, die auch in der ersten Sequenz vorhanden sind, werden diese Elemente aus der zurückgegebenen Sequenz entfernt.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>

Ein IEqualityComparer<T> zum Vergleichen von Werten.An IEqualityComparer<T> to compare values.

Gibt zurück

IEnumerable<TSource>

Eine Sequenz, die die Differenzmenge der Elemente von zwei Sequenzen enthält.A sequence that contains the set difference of the elements of two sequences.

Ausnahmen

first oder second ist null.first or second is null.

Beispiele

Wenn Sie Sequenzen von Objekten eines benutzerdefinierten Datentyps vergleichen möchten, müssen Sie die IEqualityComparer<T> generische-Schnittstelle in einer Hilfsklasse implementieren.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. Im folgenden Codebeispiel wird veranschaulicht, wie Sie diese Schnittstelle in einem benutzerdefinierten Datentyp Equals implementieren und die-und-Methoden bereitstellen GetHashCode .The following code example shows how to implement this interface in a custom data type and provide GetHashCode and Equals methods. Im folgenden Beispiel wird gezeigt, wie ein Gleichheits Vergleich implementiert wird, der in der Except -Methode verwendet werden kann.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

Nachdem Sie diesen Vergleich implementiert haben, können Sie Sequenzen von Product Objekten in der Except -Methode verwenden, wie im folgenden Beispiel gezeigt: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

Hinweise

Wenn comparerden Wert Defaulthat, wird der Standard Gleichheits Vergleich verwendet, um Werte zu vergleichen. nullIf comparer is null, the default equality comparer, Default, is used to compare values.

Gilt für: