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Enumerable.First(Of TSource) Method (IEnumerable(Of TSource))

Returns the first element of a sequence.

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

'Declaration
<ExtensionAttribute> _
Public Shared Function First(Of TSource) ( _
	source As IEnumerable(Of TSource) _
) As TSource

Type Parameters

TSource

The type of the elements of source.

Parameters

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

The IEnumerable(Of T) to return the first element of.

Return Value

Type: TSource
The first element in the specified sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of 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 is Nothing.

InvalidOperationException

The source sequence is empty.

The First(Of TSource)(IEnumerable(Of TSource)) method throws an exception if source contains no elements. To instead return a default value when the source sequence is empty, use the FirstOrDefault method.

The following code example demonstrates how to use First(Of TSource)(IEnumerable(Of TSource)) to return the first element of an array.

        ' 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. 
        Dim first As Integer = numbers.First()

        ' Display the output.
        MsgBox(first)

        ' This code produces the following output: 
        
        ' 9

.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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