Single(TSource) Method (IEnumerable(TSource))

Enumerable.Single(TSource) Method (IEnumerable(TSource))

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)

JScript does not support generic types or methods.

Type Parameters


The type of the elements of 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.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(TSource). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).


source is a null reference (Nothing in Visual Basic).


The input sequence contains more than one element.


The input sequence is empty.

The Single(TSource)(IEnumerable(TSource)) method throws an exception if the input sequence is empty. To instead return a null reference (Nothing in Visual Basic) when the input sequence is empty, use SingleOrDefault.

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.

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

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0

Community Additions

© 2015 Microsoft