EnumerableFirst Method
 

Returns the first element in a sequence that satisfies a specified condition.

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

Syntax
public static TSource First<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, bool> predicate
)
public:
generic<typename TSource>
[ExtensionAttribute]
static TSource First(
	IEnumerable<TSource>^ source,
	Func<TSource, bool>^ predicate
)
static member First<'TSource> : 
        source:IEnumerable<'TSource> *
        predicate:Func<'TSource, bool> -> 'TSource
<ExtensionAttribute>
Public Shared Function First(Of TSource) (
	source As IEnumerable(Of TSource),
	predicate As Func(Of TSource, Boolean)
) As TSource

Parameters

source
Type:

An IEnumerable to return an element from.

predicate
Type:

A function to test each element for a condition.

Return Value

Type: TSource

The first element in the sequence that passes the test in the specified predicate function.

Type Parameters

TSource

The type of the elements of source.

Exceptions
Exception Condition
ArgumentNullException

source or predicate is null.

InvalidOperationException

No element satisfies the condition in predicate.

-or-

The source sequence is empty.

Remarks

The First method throws an exception if no matching element is found in source. To instead return a default value when no matching element is found, use the FirstOrDefault method.

Examples

The following code example demonstrates how to use First to return the first element of an array that satisfies a condition.

int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54, 
                    83, 23, 87, 435, 67, 12, 19 };

int first = numbers.First(number => number > 80);

Console.WriteLine(first);

/*
 This code produces the following output:

 92
*/
' Create an array of integers.
Dim numbers() As Integer = _
    {9, 34, 65, 92, 87, 435, 3, 54, 83, 23, 87, 435, 67, 12, 19}

' Select the first element in the array whose value is greater than 80.
Dim first As Integer = numbers.First(Function(number) number > 80)

' Display the output.
MsgBox(first)

' This code produces the following output:
'
' 92
Version Information
Universal Windows Platform
Available since 4.5
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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