Enumerable.Contains Metoda

Definice

Určuje, zda sekvence obsahuje zadaný element.Determines whether a sequence contains a specified element.

Přetížení

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

Určuje, zda sekvence obsahuje zadaný element pomocí výchozí porovnávače rovnosti.Determines whether a sequence contains a specified element by using the default equality comparer.

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

Určuje, zda sekvence obsahuje zadaný element pomocí zadaného prvku IEqualityComparer<T> .Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

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

Určuje, zda sekvence obsahuje zadaný element pomocí výchozí porovnávače rovnosti.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

Parametry typu

TSource

Typ prvků source .The type of the elements of source.

Parametry

source
IEnumerable<TSource>

Sekvence, ve které se má vyhledat hodnotaA sequence in which to locate a value.

value
TSource

Hodnota, která má být v sekvenci nalezena.The value to locate in the sequence.

Návraty

Boolean

true Pokud zdrojová sekvence obsahuje element, který má zadanou hodnotu; v opačném případě false .true if the source sequence contains an element that has the specified value; otherwise, false.

Výjimky

source je null.source is null.

Příklady

Následující příklad kódu ukazuje, jak použít Contains<TSource>(IEnumerable<TSource>, TSource) k určení, zda pole obsahuje konkrétní prvek.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

Poznámky

Pokud typ source Implements ICollection<T> , Contains metoda v této implementaci je vyvolána pro získání výsledku.If the type of source implements ICollection<T>, the Contains method in that implementation is invoked to obtain the result. V opačném případě tato metoda určuje, zda source obsahuje zadaný element.Otherwise, this method determines whether source contains the specified element.

Výčet se ukončí hned po nalezení odpovídajícího prvku.Enumeration is terminated as soon as a matching element is found.

Prvky jsou porovnány se zadanou hodnotou pomocí výchozí porovnávače rovnosti Default .Elements are compared to the specified value by using the default equality comparer, Default.

Platí pro

Produkt Introduced

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

Určuje, zda sekvence obsahuje zadaný element pomocí zadaného prvku IEqualityComparer<T> .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

Parametry typu

TSource

Typ prvků source .The type of the elements of source.

Parametry

source
IEnumerable<TSource>

Sekvence, ve které se má vyhledat hodnotaA sequence in which to locate a value.

value
TSource

Hodnota, která má být v sekvenci nalezena.The value to locate in the sequence.

comparer
IEqualityComparer<TSource>

Porovnávání rovnosti pro porovnání hodnot.An equality comparer to compare values.

Návraty

Boolean

true Pokud zdrojová sekvence obsahuje element, který má zadanou hodnotu; v opačném případě false .true if the source sequence contains an element that has the specified value; otherwise, false.

Výjimky

source je null.source is null.

Příklady

Následující příklad ukazuje, jak implementovat porovnávání rovnosti, které lze použít v Contains metodě.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

Po implementaci této porovnávací metody můžete použít sekvenci Product objektů v Contains metodě, jak je znázorněno v následujícím příkladu: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

Poznámky

Výčet se ukončí hned po nalezení odpovídajícího prvku.Enumeration is terminated as soon as a matching element is found.

Pokud comparer je null , použije se výchozí porovnávání rovnosti Default pro porovnání prvků se zadanou hodnotou.If comparer is null, the default equality comparer, Default, is used to compare elements to the specified value.

Platí pro

Produkt Introduced