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.
Namespace: System.Linq
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.| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
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.
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