Queryable.Single Queryable.Single Queryable.Single Queryable.Single Method

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>(IQueryable<TSource>) Single<TSource>(IQueryable<TSource>) Single<TSource>(IQueryable<TSource>) Single<TSource>(IQueryable<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>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) Single<TSource>(IQueryable<TSource>, Expression<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>(IQueryable<TSource>) Single<TSource>(IQueryable<TSource>) Single<TSource>(IQueryable<TSource>) Single<TSource>(IQueryable<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::Linq::IQueryable<TSource> ^ source);
public static TSource Single<TSource> (this System.Linq.IQueryable<TSource> source);
static member Single : System.Linq.IQueryable<'Source> -> 'Source
<Extension()>
Public Function Single(Of TSource) (source As IQueryable(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
IQueryable<TSource>

IQueryable<T>の 1 つの要素を返します。An IQueryable<T> to return the single element of.

戻り値

TSource TSource TSource TSource

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

例外

source 複数の要素があります。source has more than one element.

次のコード例は、使用する方法を示しますSingle<TSource>(IQueryable<TSource>)を配列の唯一の要素を選択します。The following code example demonstrates how to use Single<TSource>(IQueryable<TSource>) to select the only element of an array.

// Create two arrays.
string[] fruits1 = { "orange" };
string[] fruits2 = { "orange", "apple" };

// Get the only item in the first array.
string fruit1 = fruits1.AsQueryable().Single();

Console.WriteLine("First query: " + fruit1);

try
{
    // Try to get the only item in the second array.
    string fruit2 = fruits2.AsQueryable().Single();
    Console.WriteLine("Second query: " + fruit2);
}
catch (System.InvalidOperationException)
{
    Console.WriteLine(
        "Second query: The collection does not contain exactly one element."
        );
}

/*
    This code produces the following output:

    First query: orange
    Second query: The collection does not contain exactly one element
*/

' Create two arrays.
Dim fruits1() As String = {"orange"}
Dim fruits2() As String = {"orange", "apple"}

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

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

Try
    ' Try to get the only item in the second array.
    Dim fruit2 As String = fruits2.AsQueryable().Single()
    MsgBox("Second query: " + fruit2)
Catch
    MsgBox("Second query: The collection does not contain exactly one element.")
End Try

' This code produces the following output:

' First query: orange
' Second query: The collection does not contain exactly one element.

注釈

Single<TSource>(IQueryable<TSource>)メソッドを生成、MethodCallExpression呼び出しを表すSingle<TSource>(IQueryable<TSource>)として構築されたジェネリック メソッド自体。The Single<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Single<TSource>(IQueryable<TSource>) itself as a constructed generic method. これは、後、渡します、MethodCallExpressionExecute<TResult>(Expression)のメソッド、IQueryProviderによって表される、Providerのプロパティ、sourceパラメーター。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

呼び出し元を表す式ツリーを実行した結果として発生するクエリの動作Single<TSource>(IQueryable<TSource>)の型の実装によって異なります、sourceパラメーター。The query behavior that occurs as a result of executing an expression tree that represents calling Single<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. 想定される動作では、唯一の要素を返しますsourceします。The expected behavior is that it returns the only element in source.

Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) Single<TSource>(IQueryable<TSource>, Expression<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::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, bool> ^> ^ predicate);
public static TSource Single<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,bool>> predicate);
static member Single : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, bool>> -> 'Source
<Extension()>
Public Function Single(Of TSource) (source As IQueryable(Of TSource), predicate As Expression(Of 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
IQueryable<TSource>

IQueryable<T>から 1 つの要素を返します。An IQueryable<T> to return a single element from.

predicate
Expression<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 TSource TSource TSource

1 つの要素の条件を満たす入力シーケンスのpredicateします。The single element of the input sequence that satisfies the condition in predicate.

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- 1 つ以上の要素が条件を満たすpredicateします。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.

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

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

// Get the only string in the array whose length is greater than 10.
string fruit1 = fruits.AsQueryable().Single(fruit => fruit.Length > 10);

Console.WriteLine("First Query: " + fruit1);

try
{
    // Try to get the only string in the array
    // whose length is greater than 15.
    string fruit2 = fruits.AsQueryable().Single(fruit => fruit.Length > 15);
    Console.WriteLine("Second Query: " + fruit2);
}
catch (System.InvalidOperationException)
{
    Console.Write("Second Query: The collection does not contain ");
    Console.WriteLine("exactly one element whose length is greater than 15.");
}

/*
    This code produces the following output:

    First Query: passionfruit
    Second Query: The collection does not contain exactly one 
    element whose length is greater than 15.
 */

Dim fruits() As String = _
    {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

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

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

Try
    ' Try to get the only string in the array
    ' whose length is greater than 15.
    Dim fruit2 As String = fruits.AsQueryable().Single(Function(fruit) fruit.Length > 15)
    MsgBox("Second Query: " + fruit2)
Catch
    Dim text As String = "Second Query: The collection does not contain "
    text = text & "exactly one element whose length is greater than 15."
    MsgBox(text)
End Try

' This code produces the following output:

' First Query: passionfruit
' Second Query: The collection does not contain exactly one 
'   element whose length is greater than 15.

注釈

このメソッドは、少なくとも 1 つのパラメーター型のExpression<TDelegate>型引数は、のいずれか、Func<T,TResult>型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. ラムダ式で、これらのパラメーターを渡すことができますにコンパイルされると、Expression<TDelegate>します。For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)メソッドを生成、MethodCallExpression呼び出しを表すSingle<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)として構築されたジェネリック メソッド自体。The Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) itself as a constructed generic method. これは、後、渡します、MethodCallExpressionExecute<TResult>(Expression)のメソッド、IQueryProviderによって表される、Providerのプロパティ、sourceパラメーター。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

呼び出し元を表す式ツリーを実行した結果として発生するクエリの動作Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)の型の実装によって異なります、sourceパラメーター。The query behavior that occurs as a result of executing an expression tree that represents calling Single<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) depends on the implementation of the type of the source parameter. 想定される動作では、唯一の要素を返しますsourceによって指定された条件を満たすpredicateします。The expected behavior is that it returns the only element in source that satisfies the condition specified by predicate.

適用対象