Enumerable.Contains Metode

Definisi

Ruang nama:

System.Linq

Rakitan:

System.Linq.dll

Menentukan apakah urutan berisi elemen tertentu.

Overload

Contains<TSource>(IEnumerable<TSource>, TSource)	Menentukan apakah urutan berisi elemen tertentu dengan menggunakan perbandingan kesetaraan default.
Contains<TSource>(IEnumerable<TSource>, TSource, IEqualityComparer<TSource>)	Menentukan apakah urutan berisi elemen tertentu dengan menggunakan IEqualityComparer<T>.

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

Sumber:

Contains.cs

Menentukan apakah urutan berisi elemen tertentu dengan menggunakan perbandingan kesetaraan default.

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

Jenis parameter

TSource

Jenis elemen source.

Parameter

source

IEnumerable<TSource>

Urutan untuk menemukan nilai.

value

TSource

Nilai yang akan ditemukan dalam urutan.

Mengembalikan

Boolean

true jika urutan sumber berisi elemen yang memiliki nilai yang ditentukan; jika tidak, false.

Pengecualian

ArgumentNullException

sourceadalah null.

Contoh

Contoh kode berikut menunjukkan cara menggunakan Contains<TSource>(IEnumerable<TSource>, TSource) untuk menentukan apakah array berisi elemen tertentu.

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

Keterangan

Jika jenis source implementasi ICollection<T>, Contains metode dalam implementasi tersebut dipanggil untuk mendapatkan hasilnya. Jika tidak, metode ini menentukan apakah source berisi elemen yang ditentukan.

Enumerasi dihentikan segera setelah elemen yang cocok ditemukan.

Elemen dibandingkan dengan nilai yang ditentukan dengan menggunakan perbandingan kesetaraan default, Default.

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

Sumber:

Contains.cs

Menentukan apakah urutan berisi elemen tertentu dengan menggunakan 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);

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

Jenis parameter

TSource

Jenis elemen source.

Parameter

source

IEnumerable<TSource>

Urutan untuk menemukan nilai.

value

TSource

Nilai yang akan ditemukan dalam urutan.

comparer

IEqualityComparer<TSource>

Perbandingan kesetaraan untuk membandingkan nilai.

Mengembalikan

Boolean

true jika urutan sumber berisi elemen yang memiliki nilai yang ditentukan; jika tidak, false.

Pengecualian

ArgumentNullException

sourceadalah null.

Contoh

Contoh berikut menunjukkan cara mengimplementasikan perbandingan kesetaraan yang dapat digunakan dalam Contains metode .

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

Setelah menerapkan perbandingan ini, Anda dapat menggunakan urutan Product objek dalam Contains metode , seperti yang ditunjukkan dalam contoh berikut:

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

Keterangan

Enumerasi dihentikan segera setelah elemen yang cocok ditemukan.

Jika comparer adalah null, perbandingan kesetaraan default, Default, digunakan untuk membandingkan elemen dengan nilai yang ditentukan.