Queryable::Single<TSource> Method (IQueryable<TSource>^)

.NET Framework (current version)

Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.

Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)

Syntax

public:
generic<typename TSource>
[ExtensionAttribute]
static TSource Single(
	IQueryable<TSource>^ source
)

Parameters

source: Type: System.Linq::IQueryable<TSource>^
An IQueryable<T> to return the single element of.

Return Value

Type: TSource

The single element of the input sequence.

Type Parameters

TSource: The type of the elements of source.

Exceptions

Exception	Condition
ArgumentNullException	source is null.
InvalidOperationException	source has more than one element.

The Single<TSource>(IQueryable<TSource>^) method generates a MethodCallExpression that represents calling Single<TSource>(IQueryable<TSource>^) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression^) method of the IQueryProvider represented by the Provider property of the source parameter.

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. The expected behavior is that it returns the only element in source.

Examples

The following code example demonstrates how to use Single<TSource>(IQueryable<TSource>^) to select the only element of an array.

C++

No code example is currently available or this language may not be supported.

Version Information

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1