Enumerable.SingleOrDefault<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
Assembly: System.Core (in System.Core.dll)
public static TSource SingleOrDefault<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate )
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> to return a single element from.
- predicate
- Type: System.Func<TSource, Boolean>
A function to test an element for a condition.
Return Value
Type: TSourceThe single element of the input sequence that satisfies the condition, or default(TSource) if no such element is found.
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).| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
| InvalidOperationException | More than one element satisfies the condition in predicate. |
The following code example demonstrates how to use SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) to select the only element of an array that satisfies a condition.
The following code example demonstrates that SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) returns a default value when the sequence does not contain exactly one element that satisfies the condition.
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.