Enumerable.Contains Enumerable.Contains Enumerable.Contains Enumerable.Contains Method

定義

指定した要素がシーケンスに格納されているかどうかを調べます。Determines whether a sequence contains a specified element.

オーバーロード

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

既定の等値比較子を使用して、指定した要素がシーケンスに含まれているかどうかを判断します。Determines whether a sequence contains a specified element by using the default equality comparer.

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

指定した IEqualityComparer<T> を使用して、指定した要素がシーケンスに含まれているかどうかを判断します。Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

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

既定の等値比較子を使用して、指定した要素がシーケンスに含まれているかどうかを判断します。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

型パラメーター

TSource

source の要素の型。The type of the elements of source.

パラメーター

source
IEnumerable<TSource>

値の検索対象となるシーケンス。A sequence in which to locate a value.

value
TSource TSource TSource TSource

シーケンス内で検索する値。The value to locate in the sequence.

戻り値

指定した値を持つ要素がソース シーケンスに含まれている場合は true。それ以外は falsetrue if the source sequence contains an element that has the specified value; otherwise, false.

例外

次のコード例は、を使用Contains<TSource>(IEnumerable<TSource>, TSource)して、配列に特定の要素が含まれているかどうかを確認する方法を示しています。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.
MsgBox("The array " & text & " contain " & fruit)

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

注釈

source型がを実装ICollection<T>してContainsいる場合、その実装のメソッドが呼び出され、結果が取得されます。If the type of source implements ICollection<T>, the Contains method in that implementation is invoked to obtain the result. それ以外の場合、このsourceメソッドは指定された要素がに含まれるかどうかを判断します。Otherwise, this method determines whether source contains the specified element.

列挙は、一致する要素が見つかるとすぐに終了します。Enumeration is terminated as soon as a matching element is found.

既定の等値比較子をDefault使用して、指定した値と要素が比較されます。Elements are compared to the specified value by using the default equality comparer, Default.

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

指定した IEqualityComparer<T> を使用して、指定した要素がシーケンスに含まれているかどうかを判断します。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);
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

型パラメーター

TSource

source の要素の型。The type of the elements of source.

パラメーター

source
IEnumerable<TSource>

値の検索対象となるシーケンス。A sequence in which to locate a value.

value
TSource TSource TSource TSource

シーケンス内で検索する値。The value to locate in the sequence.

comparer
IEqualityComparer<TSource>

値を比較する等値比較子。An equality comparer to compare values.

戻り値

指定した値を持つ要素がソース シーケンスに含まれている場合は true。それ以外は falsetrue if the source sequence contains an element that has the specified value; otherwise, false.

例外

次の例は、 Containsメソッドで使用できる等値比較子を実装する方法を示しています。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

この比較子を実装した後、次の例Productに示すようContainsに、メソッドでオブジェクトのシーケンスを使用できます。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

注釈

列挙は、一致する要素が見つかるとすぐに終了します。Enumeration is terminated as soon as a matching element is found.

Defaultcomparernull場合は、既定の等値比較子 () を使用して、指定した値と要素を比較します。If comparer is null, the default equality comparer, Default, is used to compare elements to the specified value.

適用対象