Enumerable.Contains Méthode

Définition

Détermine si une séquence contient un élément spécifié.Determines whether a sequence contains a specified element.

Surcharges

Contains<TSource>(IEnumerable<TSource>, TSource)

Détermine si une séquence contient un élément spécifié à l'aide du comparateur d'égalité par défaut.Determines whether a sequence contains a specified element by using the default equality comparer.

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

Détermine si une séquence contient un élément spécifié à l'aide du IEqualityComparer<T> indiqué.Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

Contains<TSource>(IEnumerable<TSource>, TSource)

Détermine si une séquence contient un élément spécifié à l'aide du comparateur d'égalité par défaut.Determines whether a sequence contains a specified element by using the default equality comparer.

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

Paramètres de type

TSource

Le type des éléments de source.The type of the elements of source.

Paramètres

source
IEnumerable<TSource>

Séquence dans laquelle localiser une valeur.A sequence in which to locate a value.

value
TSource

Valeur à localiser dans la séquence.The value to locate in the sequence.

Retours

Boolean

true si la séquence source contient un élément avec la valeur spécifiée ; sinon, false.true if the source sequence contains an element that has the specified value; otherwise, false.

Exceptions

source a la valeur null.source is null.

Exemples

L’exemple de code suivant montre comment utiliser Contains<TSource>(IEnumerable<TSource>, TSource) pour déterminer si un tableau contient un élément spécifique.The following code example demonstrates how to use Contains<TSource>(IEnumerable<TSource>, TSource) to determine whether an array contains a specific element.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

string fruit = "mango";

bool hasMango = fruits.Contains(fruit);

Console.WriteLine(
    "The array {0} contain '{1}'.",
    hasMango ? "does" : "does not",
    fruit);

// This code produces the following output:
//
// The array does contain 'mango'.
' Create an array of strings.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' This is the string to search the array for.
Dim fruit As String = "mango"

' Determine if the array contains the specified string.
Dim hasMango As Boolean = fruits.Contains(fruit)

Dim text As String = IIf(hasMango, "does", "does not")

' Display the output.
Console.WriteLine($"The array {text} contain {fruit}")

' This code produces the following output:
'
' The array does contain mango

Remarques

Si le type de source implémente ICollection<T> , la Contains méthode de cette implémentation est appelée pour obtenir le résultat.If the type of source implements ICollection<T>, the Contains method in that implementation is invoked to obtain the result. Sinon, cette méthode détermine si source contient l’élément spécifié.Otherwise, this method determines whether source contains the specified element.

L’énumération se termine dès qu’un élément correspondant est trouvé.Enumeration is terminated as soon as a matching element is found.

Les éléments sont comparés à la valeur spécifiée à l’aide du comparateur d’égalité par défaut, Default .Elements are compared to the specified value by using the default equality comparer, Default.

S’applique à

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

Détermine si une séquence contient un élément spécifié à l'aide du IEqualityComparer<T> indiqué.Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

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

Paramètres de type

TSource

Le type des éléments de source.The type of the elements of source.

Paramètres

source
IEnumerable<TSource>

Séquence dans laquelle localiser une valeur.A sequence in which to locate a value.

value
TSource

Valeur à localiser dans la séquence.The value to locate in the sequence.

comparer
IEqualityComparer<TSource>

Comparateur d'égalité à l'aide duquel comparer des valeurs.An equality comparer to compare values.

Retours

Boolean

true si la séquence source contient un élément avec la valeur spécifiée ; sinon, false.true if the source sequence contains an element that has the specified value; otherwise, false.

Exceptions

source a la valeur null.source is null.

Exemples

L’exemple suivant montre comment implémenter un comparateur d’égalité qui peut être utilisé dans la Contains méthode.The following example shows how to implement an equality comparer that can be used in the Contains 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

Après avoir implémenté ce comparateur, vous pouvez utiliser une séquence d' Product objets dans la Contains méthode, comme indiqué dans l’exemple suivant :After you implement this comparer, you can use a sequence of Product objects in the Contains method, as shown in the following example:


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

Product apple = new Product { Name = "apple", Code = 9 };
Product kiwi = new Product {Name = "kiwi", Code = 8 };

ProductComparer prodc = new ProductComparer();

bool hasApple = fruits.Contains(apple, prodc);
bool hasKiwi = fruits.Contains(kiwi, prodc);

Console.WriteLine("Apple? " + hasApple);
Console.WriteLine("Kiwi? " + hasKiwi);

/*
    This code produces the following output:

    Apple? True
    Kiwi? False
*/


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

Dim apple = New Product With {.Name = "apple", .Code = 9}
Dim kiwi = New Product With {.Name = "kiwi", .Code = 8}

Dim prodc As New ProductComparer()

Dim hasApple = fruits.Contains(apple, prodc)
Dim hasKiwi = fruits.Contains(kiwi, prodc)

Console.WriteLine("Apple? " & hasApple)
Console.WriteLine("Kiwi? " & hasKiwi)


' This code produces the following output:
'
' Apple? True
' Kiwi? False

Remarques

L’énumération se termine dès qu’un élément correspondant est trouvé.Enumeration is terminated as soon as a matching element is found.

Si comparer est null , le comparateur d’égalité par défaut, Default , est utilisé pour comparer des éléments à la valeur spécifiée.If comparer is null, the default equality comparer, Default, is used to compare elements to the specified value.

S’applique à