Enumerable.First<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)

Syntax

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

public static TSource First<TSource>(
    this IEnumerable<TSource> source,
    Func<TSource, bool> 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.

Exceptions

Remarks

The First<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) 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<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) to return the first element of an array that satisfies a condition.

      ' 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.
      outputBlock.Text &= first & vbCrLf

      ' This code produces the following output:
      '
      ' 92

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

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

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

      /*
       This code produces the following output:

       92
      */

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.

See Also

Reference