Enumerable.Single メソッド

定義

シーケンスの 1 つの特定の要素を返します。Returns a single, specific element of a sequence.

オーバーロード

Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

指定された条件を満たす、シーケンスの唯一の要素を返し、そのような要素が複数存在する場合は例外をスローします。Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.

Single<TSource>(IEnumerable<TSource>)

シーケンスの唯一の要素を返し、シーケンス内の要素が 1 つだけでない場合は例外をスローします。Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.

Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

指定された条件を満たす、シーケンスの唯一の要素を返し、そのような要素が複数存在する場合は例外をスローします。Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.

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

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>

1 つの要素を返す IEnumerable<T>An IEnumerable<T> to return a single element from.

predicate
Func<TSource,Boolean>

要素が条件を満たしているかどうかをテストする関数。A function to test an element for a condition.

戻り値

TSource

条件を満たす、入力シーケンスの 1 つの要素。The single element of the input sequence that satisfies a condition.

例外

source または predicatenull です。source or predicate is null.

predicate の条件を満たす要素はありません。No element satisfies the condition in predicate.

- または --or- predicate の条件を満たす要素が複数あります。More than one element satisfies the condition in predicate.

- または --or- ソース シーケンスが空です。The source sequence is empty.

次のコード例では、Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) を使用して、条件を満たす配列の唯一の要素を選択する方法を示します。The following code example demonstrates how to use Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to select the only element of an array that satisfies a condition.

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

string fruit1 = fruits.Single(fruit => fruit.Length > 10);

Console.WriteLine(fruit1);

/*
 This code produces the following output:

 passionfruit
*/
' Create an array of strings.
Dim fruits() As String =
{"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Get the single item in the array whose length is greater than 10.
Dim result As String =
fruits.Single(Function(fruit) fruit.Length > 10)

' Display the result.
MsgBox("First query: " & result)

次のコード例では、シーケンスに条件を満たす要素が1つもまったく含まれていない場合に、Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) が例外をスローすることを示しています。The following code example demonstrates that Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) throws an exception when the sequence does not contain exactly one element that satisfies the condition.

string fruit2 = null;

try
{
    fruit2 = fruits.Single(fruit => fruit.Length > 15);
}
catch (System.InvalidOperationException)
{
    Console.WriteLine(@"The collection does not contain exactly 
                    one element whose length is greater than 15.");
}

Console.WriteLine(fruit2);

// This code produces the following output:
//
// The collection does not contain exactly  
// one element whose length is greater than 15.
result = String.Empty

' Try to get the single item in the array whose length is > 15.
Try
    result = fruits.Single(Function(fruit) _
                           fruit.Length > 15)
Catch ex As System.InvalidOperationException
    result = "There is not EXACTLY ONE element whose length is > 15."
End Try

' Display the result.
MsgBox("Second query: " & result)

' This code produces the following output:
'
' First query: passionfruit
' Second query: There is not EXACTLY ONE element whose length is > 15.

注釈

入力シーケンスに一致する要素が含まれていない場合、Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) メソッドは例外をスローします。The Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) method throws an exception if the input sequence contains no matching element. 一致する要素が見つからない場合は、代わりに null を返すには、SingleOrDefault を使用します。To instead return null when no matching element is found, use SingleOrDefault.

Single<TSource>(IEnumerable<TSource>)

シーケンスの唯一の要素を返し、シーケンス内の要素が 1 つだけでない場合は例外をスローします。Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.

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

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>

1 つの要素を返す IEnumerable<T>An IEnumerable<T> to return the single element of.

戻り値

TSource

入力シーケンスの 1 つの要素。The single element of the input sequence.

例外

sourcenullです。source is null.

入力シーケンスに複数の要素が含まれています。The input sequence contains more than one element.

- または --or-

入力シーケンスが空です。The input sequence is empty.

@No__t-0 を使用して配列の唯一の要素を選択する方法を次のコード例に示します。The following code example demonstrates how to use Single<TSource>(IEnumerable<TSource>) to select the only element of an array.

string[] fruits1 = { "orange" };

string fruit1 = fruits1.Single();

Console.WriteLine(fruit1);

/*
 This code produces the following output:

 orange
*/
' Create an array that contains one item.
Dim fruits1() As String = {"orange"}

' Get the single item in the array.
Dim result As String = fruits1.Single()

' Display the result.
MsgBox("First query: " & result)

次のコード例では、シーケンスに要素が1つだけ含まれていない場合に Single<TSource>(IEnumerable<TSource>) が例外をスローすることを示しています。The following code example demonstrates that Single<TSource>(IEnumerable<TSource>) throws an exception when the sequence does not contain exactly one element.

string[] fruits2 = { "orange", "apple" };
string fruit2 = null;

try
{
    fruit2 = fruits2.Single();
}
catch (System.InvalidOperationException)
{
    Console.WriteLine("The collection does not contain exactly one element.");
}

Console.WriteLine(fruit2);

/*
 This code produces the following output:

 The collection does not contain exactly one element.
*/
' Create an array that contains two items.
Dim fruits2() As String = {"orange", "apple"}

result = String.Empty

' Try to get the 'single' item in the array.
Try
    result = fruits2.Single()
Catch ex As System.InvalidOperationException
    result = "The collection does not contain exactly one element."
End Try

' Display the result.
MsgBox("Second query: " & result)

' This code produces the following output:
'
' First query: orange
' Second query: The collection does not contain exactly one element.

注釈

入力シーケンスが空の場合、Single<TSource>(IEnumerable<TSource>) メソッドは例外をスローします。The Single<TSource>(IEnumerable<TSource>) method throws an exception if the input sequence is empty. 入力シーケンスが空の場合に null を返すには、SingleOrDefault を使用します。To instead return null when the input sequence is empty, use SingleOrDefault.

適用対象