Duration (Pacific Standard Time):
To (Pacific Standard Time):
Impact:
  • None
User Action:
  • None
.NET Framework Class Library

Enumerable.First<TSource> Method (IEnumerable<TSource>)

Returns the first element of a sequence.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)
<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<TSource>

The IEnumerable<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<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 is null.

InvalidOperationException

The source sequence is empty.

The First<TSource>(IEnumerable<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<TSource>(IEnumerable<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

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8