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Enumerable.FirstOrDefault(TSource) Method (IEnumerable(TSource), Func(TSource, Boolean))

Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.

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

static member FirstOrDefault : 
        source:IEnumerable<'TSource> * 
        predicate:Func<'TSource, bool> -> 'TSource 

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable(TSource)

An IEnumerable(T) to return an element from.

predicate
Type: System.Func(TSource, Boolean)

A function to test each element for a condition.

Return Value

Type: TSource
default(TSource) if source is empty or if no element passes the test specified by predicate; otherwise, the first element in source that passes the test specified by predicate.

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).

ExceptionCondition
ArgumentNullException

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

The default value for reference and nullable types is a null reference (Nothing in Visual Basic).

The following code example demonstrates how to use FirstOrDefault(TSource)(IEnumerable(TSource), Func(TSource, Boolean)) by passing in a predicate. In the second call to the method, there is no element in the array that satisfies the condition.

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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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