Enumerable.Single<'TSource> Method (IEnumerable<'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

static member Single<'TSource> : 
        source:IEnumerable<'TSource> -> 'TSource

Parameters

source: Type: System.Collections.Generic.IEnumerable<'TSource>
An IEnumerable<'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	The input sequence contains more than one element. -or- The input sequence is empty.

Remarks

The Single<'TSource>(IEnumerable<'TSource>) method throws an exception if the input sequence is empty. To instead return null when the input sequence is empty, use SingleOrDefault<'TSource>.

Examples

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

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

The following code example demonstrates that Single<'TSource>(IEnumerable<'TSource>) throws an exception when the sequence does not contain exactly one element.