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

Returns the first element of a sequence.

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

Syntax

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

Type Parameters

  • TSource
    The type of the elements of source.

Parameters

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.

Exceptions

Exception Condition
ArgumentNullException

source is nulla null reference (Nothing in Visual Basic).

InvalidOperationException

The source sequence is empty.

Remarks

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.

Examples

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.
      outputBlock.Text &= first & vbCrLf

      ' This code produces the following output:
      '
      ' 9

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

      int first = numbers.First();

      outputBlock.Text += first + "\n";

      /*
       This code produces the following output:

       9
      */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.