Enumerable.Distinct Methode

Definition

Gibt unterschiedliche Elemente aus einer Sequenz zurückReturns distinct elements from a sequence.

Überlädt

Distinct<TSource>(IEnumerable<TSource>)

Gibt mithilfe des Standardgleichheitsvergleichs zum Vergleichen von Werten unterschiedliche Elemente aus einer Sequenz zurückReturns distinct elements from a sequence by using the default equality comparer to compare values.

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

Gibt mithilfe eines angegebenen IEqualityComparer<T> zum Vergleichen von Werten unterschiedliche Elemente aus einer Sequenz zurückReturns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.

Hinweise

Die Ergebnis Sequenz ist nicht geordnet.The result sequence is unordered.

Distinct<TSource>(IEnumerable<TSource>)

Gibt mithilfe des Standardgleichheitsvergleichs zum Vergleichen von Werten unterschiedliche Elemente aus einer Sequenz zurückReturns distinct elements from a sequence by using the default equality comparer to compare values.

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

Typparameter

TSource

Der Typ der Elemente von source.The type of the elements of source.

Parameter

source
IEnumerable<TSource>

Die Sequenz, aus der doppelte Elemente entfernt werden sollen.The sequence to remove duplicate elements from.

Gibt zurück

IEnumerable<TSource>

Ein IEnumerable<T>, das unterschiedliche Elemente aus der Quellsequenz enthältAn IEnumerable<T> that contains distinct elements from the source sequence.

Ausnahmen

source ist null.source is null.

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie Distinct<TSource>(IEnumerable<TSource>) verwendet wird, um unterschiedliche Elemente aus einer Sequenz von ganzen Zahlen zurückzugeben.The following code example demonstrates how to use Distinct<TSource>(IEnumerable<TSource>) to return distinct elements from a sequence of integers.

List<int> ages = new List<int> { 21, 46, 46, 55, 17, 21, 55, 55 };

IEnumerable<int> distinctAges = ages.Distinct();

Console.WriteLine("Distinct ages:");

foreach (int age in distinctAges)
{
    Console.WriteLine(age);
}

/*
 This code produces the following output:

 Distinct ages:
 21
 46
 55
 17
*/
' Create a list of integers.
Dim ages As New List(Of Integer)(New Integer() _
                             {21, 46, 46, 55, 17, 21, 55, 55})

' Select the unique numbers in the List.
Dim distinctAges As IEnumerable(Of Integer) = ages.Distinct()

Dim output As New System.Text.StringBuilder("Distinct ages:" & vbCrLf)
For Each age As Integer In distinctAges
    output.AppendLine(age)
Next

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

' This code produces the following output:
'
' Distinct ages:
' 21
' 46
' 55
' 17

Wenn Sie unterschiedliche Elemente aus Sequenzen von Objekten eines benutzerdefinierten Datentyps zurückgeben möchten, müssen Sie den IEquatable<T> generischen Schnittstelle in der Klasse implementieren.If you want to return distinct elements from sequences of objects of some custom data type, you have to implement the IEquatable<T> generic interface in the class. Im folgenden Codebeispiel wird gezeigt, wie diese Schnittstelle in einem benutzerdefinierten Datentyp implementiert wird und GetHashCode-und Equals Methoden bereitgestellt werden.The following code example shows how to implement this interface in a custom data type and provide GetHashCode and Equals methods.

public class Product : IEquatable<Product>
{
    public string Name { get; set; }
    public int Code { get; set; }

    public bool Equals(Product other)
    {

        //Check whether the compared object is null. 
        if (Object.ReferenceEquals(other, null)) return false;

        //Check whether the compared object references the same data. 
        if (Object.ReferenceEquals(this, other)) return true;

        //Check whether the products' properties are equal. 
        return Code.Equals(other.Code) && Name.Equals(other.Name);
    }

    // If Equals() returns true for a pair of objects  
    // then GetHashCode() must return the same value for these objects. 

    public override int GetHashCode()
    {

        //Get hash code for the Name field if it is not null. 
        int hashProductName = Name == null ? 0 : Name.GetHashCode();

        //Get hash code for the Code field. 
        int hashProductCode = Code.GetHashCode();

        //Calculate the hash code for the product. 
        return hashProductName ^ hashProductCode;
    }
}
Public Class Product
    Implements IEquatable(Of Product)

    Public Property Name As String
    Public Property Code As Integer

    Public Function Equals1(
        ByVal other As Product
        ) As Boolean Implements IEquatable(Of Product).Equals

        ' Check whether the compared object is null.
        If other Is Nothing Then Return False

        ' Check whether the compared object references the same data.
        If Me Is Other Then Return True

        ' Check whether the products' properties are equal.
        Return Code.Equals(other.Code) AndAlso Name.Equals(other.Name)
    End Function

    Public Overrides Function GetHashCode() As Integer

        ' Get hash code for the Name field if it is not null.
        Dim hashProductName = If(Name Is Nothing, 0, Name.GetHashCode())

        ' Get hash code for the Code field.
        Dim hashProductCode = Code.GetHashCode()

        ' Calculate the hash code for the product.
        Return hashProductName Xor hashProductCode
    End Function
End Class

Nachdem Sie diese Schnittstelle implementiert haben, können Sie eine Sequenz von Product Objekten in der Distinct<TSource>(IEnumerable<TSource>)-Methode verwenden, wie im folgenden Beispiel gezeigt:After you implement this interface, you can use a sequence of Product objects in the Distinct<TSource>(IEnumerable<TSource>) method, as shown in the following example:

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

//Exclude duplicates.

IEnumerable<Product> noduplicates =
    products.Distinct();

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

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

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

' Exclude duplicates.

Dim noduplicates = products.Distinct()

For Each product In noduplicates
    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 ausgeführt, wenn das Objekt durch Aufrufen der GetEnumerator Methode direkt oder mithilfe foreach in der Visualisierung C# oder For Each in Visual Basic aufgezählt 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.

Die Distinct<TSource>(IEnumerable<TSource>)-Methode gibt eine ungeordnete Sequenz zurück, die keine doppelten Werte enthält.The Distinct<TSource>(IEnumerable<TSource>) method returns an unordered sequence that contains no duplicate values. Er verwendet den Standard Gleichheits Vergleich, Default, um Werte zu vergleichen.It uses the default equality comparer, Default, to compare values.

In Visual Basic Abfrage Ausdruckssyntax wird eine Distinct-Klausel in einen Aufruf von Distinctübersetzt.In Visual Basic query expression syntax, a Distinct clause translates to an invocation of Distinct.

Der Standard Gleichheits Vergleich, Default, wird zum Vergleichen von Werten der Typen verwendet, die die IEquatable<T> generische Schnittstelle implementieren.The default equality comparer, Default, is used to compare values of the types that implement the IEquatable<T> generic interface. Um einen benutzerdefinierten Datentyp zu vergleichen, müssen Sie diese Schnittstelle implementieren und ihre eigenen GetHashCode und Equals Methoden für den-Typ bereitstellen.To compare a custom data type, you need to implement this interface and provide your own GetHashCode and Equals methods for the type.

Ein Beispiel, in dem IEqualityComparer<T> zum Definieren eines benutzerdefinierten Vergleichs verwendet wird, finden Sie unter Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>).For an example that uses IEqualityComparer<T> to define a custom comparer, see Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>).

Siehe auch

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

Gibt mithilfe eines angegebenen IEqualityComparer<T> zum Vergleichen von Werten unterschiedliche Elemente aus einer Sequenz zurückReturns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.

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

Typparameter

TSource

Der Typ der Elemente von source.The type of the elements of source.

Parameter

source
IEnumerable<TSource>

Die Sequenz, aus der doppelte Elemente entfernt werden sollen.The sequence to remove duplicate elements from.

comparer
IEqualityComparer<TSource>

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

Gibt zurück

IEnumerable<TSource>

Ein IEnumerable<T>, das unterschiedliche Elemente aus der Quellsequenz enthältAn IEnumerable<T> that contains distinct elements from the source sequence.

Ausnahmen

source ist null.source is null.

Beispiele

Im folgenden Beispiel wird gezeigt, wie ein Gleichheits Vergleich implementiert wird, der in der Distinct-Methode verwendet werden kann.The following example shows how to implement an equality comparer that can be used in the Distinct 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 eine Sequenz von Product Objekten in der Distinct-Methode verwenden, wie im folgenden Beispiel gezeigt:After you implement this comparer, you can use a sequence of Product objects in the Distinct method, as shown in the following example:

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

//Exclude duplicates.

IEnumerable<Product> noduplicates =
    products.Distinct(new ProductComparer());

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

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

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

' Exclude duplicates.

Dim noduplicates = products.Distinct(New ProductComparer())

For Each product In noduplicates
    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 ausgeführt, wenn das Objekt durch Aufrufen der GetEnumerator Methode direkt oder mithilfe foreach in der Visualisierung C# oder For Each in Visual Basic aufgezählt 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.

Die Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)-Methode gibt eine ungeordnete Sequenz zurück, die keine doppelten Werte enthält.The Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) method returns an unordered sequence that contains no duplicate values. Wenn comparer nullist, wird der Standard Gleichheits Vergleich (Default) verwendet, um Werte zu vergleichen.If comparer is null, the default equality comparer, Default, is used to compare values.

Gilt für: